How To Fix TPDA661 - A terminal ID for outgoing requests could not be set.

SAP Error Message - Details

• Message type: E = Error

• Message class: TPDA - Debugger

• Message number: 661

• Message text: A terminal ID for outgoing requests could not be set.

What causes this issue?

No terminal ID could be determined for outgoing requests.
It is possible that you did not start the action that led to this
message in a SAP GUI window (e.g. Web GUI). Use SAP GUI for Windows,
since otherwise this function does not exist.
It is possible that you also have not yet set an external breakpoint
which is associated with a terminal ID. In the ABAP Workbench, select
the terminal ID activation for external bugging under:
Utilities -> Settings -> ABAP Editor -> Debugging
Breakpoints set after this will then be associated with this terminal
ID. It is then also possible to run any number of external sessions (SAP
GUI windows) in the same Windows logon automatically with this terminal
ID for outgoing requests (OK code: "/HTID").

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.