Purchase requisition from sales document' not possible due to a credit bloc

hi experts,

i have to confirm delivery date and quantity for some purchase order items but i'm not able because i receive following message:

Subsequent function 'Purchase requisition from sales document' not possible due to a credit block' 

Purchase requisition belongs to a sales order which has customer 10000.

The customer 10000 was block from FD32 but now i have unblock the customer from FD32, i have assigned customer to a category risk which is only a warning. (in OVA8 risk category 002 static check, reaction C, status/block uncheck )

There is any possiblilities to confirm quantity ?? I mean ... i understand that sales order was created when the customer was block due to credit limit exceded ... but now the customer is not blocked.

What should i do?

Thank you.