Synology NAS

[the_bertrum]

One thing to check, is that the SMB version mount flags (specifically the VERS= ) is compatible with the minimum SMB protocol version specified on your Synology NAS. 

In the Synology NAS DSM, the SMB versions are specified here:
Control Panel -> File Services -> SMB Tab -> Advanced Settings
Maximum SMB Protocol  -> SMB3 (or whatever is appropriate for your network)
Minimum SMB Protocol -> SMB2 (or whatever is appropriate for your network)

So in the above case, the Moode SMB Mount flag should specify:
VERS=2.0  or  3.0   as the values are within the maximum and minimum values specified on the NAS.

The default value of 1.0 would/should not work in the above case, so you need to check your specified values on your NAS to discern the proper flag value.
(FYI, use of SMB1 has been discouraged for a number of years)

Alternatively, the vers= flag can be left off the string and moOde will negotiate the highest mutually compatible version.