Posting free text invoice disabled suddenly

Hi all

I have approve workflow enabled for free text invoice, and I am using it normally and post the invoice normally without problems.

Suddenly I found the post button in free text invoice disabled for any new invoices.

Then I created another version for the workflow and it works fine, but after 2 days the posting was disabled again.

Does anyone know what is the problem?

I have AX 2012 R2 CU7

Thanks