I can program chips on a breadboard, but can't when they're in an Uno

I bought a few atmega328p-pu's for some projects. I loaded bootloaders onto them via an Uno and a breadboard. No issues there. I can also upload sketches to them through the Uno to the chip on the breadboard. No issues. They work fine and run the sketches fine as standalone chips on a breadboard or soldered on a circuit board. The problem is when I take one of these chips and put it into an Uno. When I do that the code runs and it seems OK, but I can't upload any sketch updates, or new code to it when it's on the Uno board. I've tried an authentic Arduino Uno board and a cheap off brand one as well. Same results. If I take the chip out of the Uno and put it back on the breadboard, I can again update the sketches.

Any ideas??

The erros I get when trying to upload a sketch while the chip is in the board are like this:

avrdude: Version 6.3, compiled on Jul 12 2018 at 21:00:17
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/etc/avrdude/avrdude.conf"
         User configuration file is "/home/nick/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyACM4
         Using Programmer              : arduino
         Overriding Baud Rate          : 57600
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

If you uploaded a sketch using an ISP programmer, you erased the bootloader. Program the chip with the bootloader only, then try it on the uno board.

Thank you so much, David! That was the piece of information I was missing. The chips now work on the Uno boards.

NIck