avrdude: stk500_recv(): programmer is not responding UNO

Upgraded to macOS Catalina. Latest version of IDE. Tried nightly build and Beta.
Been using the IDE for years without issue.
Now can’t load Blink sketch to either of two UNO’s, however works fine uploading to Nano (old boot loader) and to Mega. Can load sketches to UNO’s using my Windows 10 laptop, but not using the Mac.

Am able to get board info OK.

BN: Arduino Uno
VID: 2341
PID: 0043
SN: 854363236313518172A0
Arduino: 1.8.13 Hourly Build 2020/03/25 04:12 (Mac OS X), Board: "Arduino Uno"

Sketch uses 924 bytes (2%) of program storage space. Maximum is 32256 bytes.
Global variables use 9 bytes (0%) of dynamic memory, leaving 2039 bytes for local variables. Maximum is 2048 bytes.
/Applications/Arduino.app/Contents/Java/hardware/tools/avr/bin/avrdude -C/Applications/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf -v -patmega328p -carduino -P/dev/cu.usbmodem4101 -b115200 -D -Uflash:w:/var/folders/fw/vmyqzfpx6fnddfbgb5yyxfdw0000gn/T/arduino_build_115569/Blink.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 "/Applications/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/Users/anthony/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/cu.usbmodem4101
         Using Programmer              : arduino
         Overriding Baud Rate          : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude done.  Thank you.

Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

So, given all the other posts everywhere about problems people have been having with Catalina (I'm running 10.15.3) and the fact that my kit works fine on a PC, just not on my Mac, is the general consensus that there are still problems with Catalina and the Arduino IDE and Uno's? If so, I will just wait until someone fixes it. If no-one else has a problem, then I need to keep investigating. Odd that it is just the two Uno's and not my Nano or Mega.