A. You are not the currency record owner.
B. The currency is used by an active business process.
C. The currency is the base currency.
D. The currency is used by another record.
Explanation:
Reference:
https://docs.microsoft.com/en-us/powerapps/developer/data-platform/org-service/web-service-error-codes
https://docs.microsoft.com/en-us/power-platform/admin/manage-transactions-with-multiple-currencies