You haven't told us anything about the software you are using to share the drive (ie. what is your NAS on 192.168.1.20).
Is it a LibreELEC host? Or Windows? Or something else? What version of whatever software are you using?
It looks to me like SMB3 is either not supported or not enabled on the NAS, so you should either enable SMB3 (if the NAS supports it) or try connecting with a lower protocol (ie. vers=2.1, vers=2.0 etc.).
If the NAS only supports SMB1 you may need to include "sec=ntlm" as an option, and of course specify "vers=1.0".