"Batch is out of balance and cannot be closed" Message

Hi everyone! I'm new to using Tessitura and I've come across a problem I'm not sure what to do with. I've been entering some contributions that span several months, and when I go to close the batch to prepare it for posting, I get a message saying the batch is out of balance and cannot be closed. The only thing is, from what I can tell, the batch is in balance. The amount I entered when I was opening the batch is equal to the amount I've entered as contributions. I've gone through each contribution multiple times and checked for errors, but I can't find anything wrong. Is this a potential system error, or should I get another pair of eyes on my batch? I appreciate the help!