Two weeks ago I Upgraded my test machine with Several Linux distros and had the same issue. I use Linux Mint 19.3 and had no issues. However when I went to Linux Mint 20 I could not access files on my net. We have a mix of 32 bit and 64 bit machines in our building because of needed software in use. It would see the machines and folders but would not mount. It seems to be an issue with the 5.4 Linux kernel and accessing files on 32 machines in the building.. I went back to Linux Mint 19.3 and all was fine. Any comments. After Mint failed I had tried Ubuntu 20.04 and even Manjero...same problem with all the upgraded OS's. I use my test machine before I load changes on the other 64 bit machines in our network.