I have 2 different nano boards. One will upload on my old computer the other will not. But the problem is just the opposite for my new computer. The nano that would not upload on the old computer will upload on the new computer. Both computers in the device manager have the same (USB-SERIAL CH340 (COM5) or which ever port I am plugged into. When they do upload the programs work fine. I am using Arduino ver 1.8.9. I don't know if it is a driver problem or what. Any help would be appreciated.
Select Tools > Processor > ATmega328P (Old Bootloader) on your new computer and then try uploading again to the Nano that won't upload. Then you'll need to switch it back to Tools > Processor > ATmega328P when you use the other Nano.
1.8.9 is getting old maybe its time for an upgrade ?
Also have you tried both bootloader options inc. the “old bootloader” when selecting the NANO ?
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