I can not connect to SMB shares after upgrading macOS from Mojave to Catalina
I had the same problem and solved it in a strange way, 
As we are all aware Mac user has actually 2 names: one is the username (the profile name if i may) and the Display name.

Prior to Catalina , when authenticating with an SMB share from a Windows computer , I was using the display name (although it is a full name with a space - strange for the traditional windows user...) and everything was cool.

In Catalina , I found out I can only use the username, windows cannot authenticate with the display name.

of course , before I got to this point I have checked/enabled SMBv2, created the NetBios file in the MAC and all the other hints I could find, which obviously did not do the trick for me.

hope this helps