By default, UGA lists have a 'message threshold' of 50 messages per day. When the number of posts exceeds the threshold, the list is put on hold until released by the owner. LISTSERV sends a message to the primary list owner when a list is held.

LISTSERV does not automatically free the list the next day, because the large number of messages may indicate a problem (anything from a mail loop to a flame war), and some owner action may be needed before normal processing should resume.

If all is well and list is just very busy, you can free it by sending the command
free name-of-your-list
to listserv@listserv.uga.edu

If there are normally something approaching 50 postings per day to your list, you can avoid having it go on 'hold' by increasing the message threshold. The list header to add is
* Daily-Threshold= nnn
See the FAQ "How do I change the header settings of my list?" for more information on updating list headers.