Upload error

My sketch was uploading fine with ctrl+shift++U.
Today it is giving an error during upload.
My code is

/*
   ATmega8@16MHz_7seg_4digit


*/

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <stdio.h>

#define LED_Directions DDRD      /* define LED Direction */
#define LED_Direction DDRB      /* define LED Direction */
#define LED_PORT1 PORTD       /* define LED port */
#define LED_PORT2 PORTB       /* define LED port */

int segments[] = {0b10111111, 0b10000110, 0b11011011, 0b11001111, 0b11100110, 0b11101101, 0b11111101, 0b10000111, 0b11111111, 0b11101111};
int k, j, i, h, factor;
int brightvalue = 0;


void set_brightness()
{
  int brightness = brightvalue;
  while (0 < brightness)
  {
    _delay_us(1);
    --brightness;
  }
}

ISR(TIMER0_OVF_vect)
{
  PORTB = (1 << PB0);
  PORTD = segments[k];
  set_brightness();

  PORTB = (1 << PB1);
  PORTD = segments[j];
  set_brightness();

  PORTB = (1 << PB2);
  PORTD = segments[i];
  set_brightness();

  PORTB = (1 << PB3);
  PORTD = segments[h];
  set_brightness();

}

void SevenSeg_SetNumber(int num)
{
  k = num % 10;
  num = num / 10;

  j = num % 10;
  num = num / 10;

  i = num % 10;
  num = num / 10;

  h = num % 10;
  num = num / 10;
}





int main(void)
{
  sei();
  DDRD = 0xff;    /* define port direction is output */
  DDRB = 0xff;   /* define port direction is output */
  PORTD = 0x00;
  PORTB = 0x00;
  TIMSK = (1 << TOIE0); /* Enable Timer0 overflow interrupts */
  TCNT0 = 0;  /* load TCNT0, count for 10ms*/
  TCCR0 = (1 << CS02); /* start timer0 with /256 prescaler*/

  brightvalue = 1000; /* set brightness level of 7 segment display */

  while (1)
  {
    SevenSeg_SetNumber(2500);/* set value to display */

  }
}

the error message is

Arduino: 1.8.11 (Windows 10), Board: "ATmega8, Yes (UART0), BOD 2.7V, LTO disabled, 16 MHz external"

D:\Arduino_1.8.11\arduino-1.8.11\arduino-builder -dump-prefs -logger=machine -hardware D:\Arduino_1.8.11\arduino-1.8.11\hardware -hardware D:\Arduino_1.8.11\arduino-"C:\\Users\\Karanbir\\AppData\\Local\\Temp\\arduino_build_138578\\sketch\\SevSegArrayTest.ino.cpp.o"
Compiling libraries...
Compiling core...
Using precompiled core: C:\Users\Karanbir\AppData\Local\Temp\arduino_cache_352303\core\core_64f4847de77d63802f23cfd9351c6407.a
D:\\Arduino_1.8.11\\arduino-1.8.11\\hardware\\tools\\avr/bin/avr-objcopy" -O ihex -R .eeprom "C:\\Users\\Karanbir\\AppData\\Local\\Temp\\arduino_build_138578/SevSegArrayTest.ino.elf" "C:\\Users\\Karanbir\\AppData\\Local\\Temp\\arduino_build_138578/SevSegArrayTest.ino.hex"
"D:\\Arduino_1.8.11\\arduino-1.8.11\\hardware\\tools\\avr/bin/avr-size" -A "C:\\Users\\Karanbir\\AppData\\Local\\Temp\\arduino_build_138578/SevSegArrayTest.ino.elf"
Sketch uses 516 bytes (6%) of program storage space. Maximum is 7680 bytes.
Global variables use 30 bytes (2%) of dynamic memory, leaving 994 bytes for local variables. Maximum is 1024 bytes.
D:\Arduino_1.8.11\arduino-1.8.11\hardware\tools\avr/bin/avrdude -CD:\Arduino_1.8.11\arduino-1.8.11\hardware\tools\avr/etc/avrdude.conf -v -patmega8 -cusbasp -Pusb -Uflash:w:C:\Users\Karanbir\AppData\Local\Temp\arduino_build_138578/SevSegArrayTest.ino.hex:i 

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "D:\Arduino_1.8.11\arduino-1.8.11\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : usb
         Using Programmer              : usbasp
         AVR Part                      : ATmega8
         Chip Erase delay              : 10000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom         4    20   128    0 no        512    4      0  9000  9000 0xff 0xff
           flash         33    10    64    0 yes      8192   64    128  4500  4500 0xff 0x00
           lfuse          0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           efuse          0     0     0    0 no          0    0      0     0     0 0x00 0x00
           lock           0     0     0    0 no          1    0      0  2000  2000 0x00 0x00
           calibration    0     0     0    0 no          4    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : usbasp
         Description     : USBasp, http://www.fischl.de/usbasp/

avrdude: auto set sck period (because given equals null)
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9307 (probably m8)
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: auto set sck period (because given equals null)
avrdude: reading input file "C:\Users\Karanbir\AppData\Local\Temp\arduino_build_138578/SevSegArrayTest.ino.hex"
avrdude: writing flash (516 bytes):

Writing | ################################################## | 100% 6.56s

avrdude: 516 bytes of flash written
avrdude: verifying flash memory against C:\Users\Karanbir\AppData\Local\Temp\arduino_build_138578/SevSegArrayTest.ino.hex:
avrdude: load data flash data from input file C:\Users\Karanbir\AppData\Local\Temp\arduino_build_138578/SevSegArrayTest.ino.hex:
avrdude: input file C:\Users\Karanbir\AppData\Local\Temp\arduino_build_138578/SevSegArrayTest.ino.hex contains 516 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 4.88s

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
         0x00 != 0x12
avrdude: verification error; content mismatch

avrdude done.  Thank you.

the selected serial port 
 does not exist or your board is not connected

I have truncated the error to fit the 9000 challenge.

I checked with previous version of IDE. It worked.
started ver 1.8.11 and it worked.
God knows where the snarl was.