I just recently bought an elegoo uno r3 off of amazon to run some small projects for class, and I was able to run about two programs with it until the board stopped showing up in my serial ports. I am working on a mac (Catalina 10.15.6), and I have already tried switching usb ports, switching boards, rebooting my mac, and manually installing the FTDI drivers, but it feels like nothing is working so this is my last-ditch effort to figure out what's going on. Is there anything else I could do?
Any help would be very appreciated.
Tried a different cable? They do go bad.
Thank for responding, I have tried another cable as well and unless both cables have gone bad (which I doubt since one is brand new), this did not solve my problem 
Does that board have an FT232 chip? I don't think it does. You may need to install the Atmega16U2 drivers.
They are located in the IDE's Arduino/drivers folder.
Altho MAC folks often say they don't need drivers. I'm on a PC.
Sometimes people have reported issues with Apples own drivers and had to install the OFFICIAL drivers to overcome Apple shortcomings.
See the posts at the top of the forum for driver links etc.
More so for CH340 drivers.
Catalina and Big Sur have introduced a lot of issues for more than just Arduino users as can be found by a search for those two items.
Bob.