For example, I have a 3825 running 12.3(14)T with no VLAN.DAT file in it's file system. It succeeds on the Running and Startup but fails on the VLAN. Generating a Partial Successful operation and the following:

VLAN Config fetch is not supported using TFTP. Command failedTELNET: Failed to establish TELNET connection to 10.x.x.x - Cause: connect timed out. VLAN Config fetch is not supported using RCP. VLAN Config fetch is not supported using SCP.

This is a different failure. RME requires the device be accessible via telnet or SSH to be able to fetch the vlan.dat. If those protocols are not available, then RME has no way to determine if the vlan.dat exists or not. Therefore, it throws an error. If, however, RME is able to login to the device successfully, it can determine if the vlan.dat really exists.

We don't use Telnet in my company, but SSH is open. I have been able to SSH from our CW box to the hosts just fine using the credentials so I know that is functional.

Make sure SSH is one of the selected protocols for config fetch under RME > Admin > Config Mgmt > Transport Settings.