The settlement receiver & is not supported.

What causes this issue?

You have maintained a distribution rule, which is supposed to settle to
a receiver that is not allowed for final settlement at this time.
A line item, which was already settled to an asset under construction
during the periodic settlement (settlement transfer) can only be
settled or capitalized to the following receivers at the present time
during the final settlement:
capitalization to completed asset
settlement to a cost center or a G/L account.

How to fix this error?

You have the following options:
Reverse the settlement/transfer, and settle the line item with a
preliminary settlement rule to the desired CO reciever.
Settle the line item during the final settlement to the allowed
receivers and then transfer this amount from these receivers to the
desired receiver.
Transfer the amount, using a CO transfer, directly from the measure to
the desired receiver. The transfer is then treated like a completely
normal line item on the measure, and is also settled to the asset under
construction during the periodic settlement.

Error message extract from SAP system. Copyright SAP SE.