You cannot switch to change mode/display mode

What causes this issue?

Switching between modes can be disallowed if:
The original language of the form is different to the logon language
when you switch to change mode
The form just created is not saved if you switch to display mode

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.