Target file of the internal link is not valid

What causes this issue?

You have specified an invalid file as a target for an internal link.

System Response

The system cancels processing.

How to fix this error?

An internal link can only be set to a file that is inside the same
attachment folder.
Specify a valid file as the target for the internal link.

Procedure for System Administrators

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.