Customer account blocked for posting.

Hi,

Recently,I have used the t.code F-21"posting without clearing" and post an incoming payment of 30,000 but afterward i am going to generate customer invoice against it by using t.code f-22......and generate an invoice of 30,000 against it...

please tell me Am I right in this regard and I have do the same as mention above?

But afterward when i move further to clear the open item by using the t.code f-32 i receive the message no F-5287 that the customer is block guide me what i have to do?