Maintain short text key & for operation & correctly

What causes this issue?

The standard text key you have entered does not exist.

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

System Response

How to fix this error?

Check whether the standard text key you have entered is correct. If it
is not, enter the correct one. You can use the possible entries
pushbutton to display a list of the standard text keys allowed.

Error message extract from SAP system. Copyright SAP SE.