For the ISO code &1 there is no unique SAP currency code for ALE

What causes this issue?

There are several entries in TCURC for this ISO code, but none with the
primary flag set.

How to fix this error?

In table TCURC set the primary flag for ISO codes used multiple times.

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.