HI Venkat
Please check if you can directly post a particular document, which you are trying to post (from parked status). If you are getting same error then it is functional issue & as mentioned by others, you need to check settings of field status groups.
Either ways, if you are posting functional area for a particular GL, then field status group should be optional. I am not sure how system would have allowed you to post in past for same.
Regards
Bhavesh