I just set up mine, after getting a bunch of errors and watching various youtube videos / forum posts, the following worked for me in the fstab:
//ServerIP/sharename /where/to/mount cifs username=username,password=yourpassword,iocharset=utf8 0 0
If you have spaces in your share directories, use:
/040
I also made everything lowercase as case seemed to matter.
If that doesn’t work, you can try this guide (I didnt need to do this):