Hello, apologies for being a dimmo but have you started with the basics?
Can machine A ping machine B? Can you ping the IP and hostnames? Is this a ‘reliable’ connection, i.e no dropped packets or weird routing? Are both machines on the same VLAN? (I’l assume they are, as that’s jjust another order of headache).
Assuming they can’t ping, the first steps would be to work out why not, and simplify your setup as much as possible until they can.
I apologise if this is sort of baby steps for a more complex issue.
I don’t know if it helps you but I had excellent support in mapping an SMB share and documented my steps here: Mounting remote SMB share directly on TrueNAS Scale - #14 by Nick