There are utilities that can be ran to update the AR's if you have not ran a final daysheet! Backup your software and contact technical support- explain the situation to them. Everyone will need to be out of softdent when you run this and make sure you have a valid backup! Ask them to check the validity of your AR #'s- there is a specific way to run the Transactions for a period report to check for balance mismatches. View the RCVTOT from List or File and look for the first date and last date on that list. Some practices had a date starting in the year 1800 or have future dates- corruptions and balance mismatches. They may need to recreate the RCVtot.dat and IDX files from all transactions. This will make sure your AR's will be correct.
Softdent will give you a message, I don't recall exactly the terminology, but you'll know. There is an utility to reset the daysheet date, in case your office is having difficulties. If you've never done that before, or never accessed the Utilities, I'd get a helping hand with Support.