FTAM error Lower layer failure

[Rajesh kumar_8]

While using FTAM from application over X.25 we are getting this error
Ftam Internal Error.FTAM Diagnostics: 1011 Negative connect confirm (without user data) from address 0x????.????.????. Verify an FTAM responder is accepting connections on the remote node (log_instance:1028, FTAM error_id 1011 = "Lower layer failure").(FTE035) Confirmation failed (FTV000) No additional information available

While we are able to connect using ftam tool to remote end and transfer the file.
Has anyone faced similar issue?

I am trying to connect to Siemens switch.

Thanks