Selection & neither G/L account nor CM group - Leading zeros missing?

What causes this issue?

The selection entered is not in the table of cash management groups
(view V_T035) or the table of G/L accounts (table SKA1).

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?

Check that the entry is correct. If the entry references a G/L account,
the error may have arisen because you did not enter the necessary
leading zeros.

Error message extract from SAP system. Copyright SAP SE.