It sounds like the "Paid Today" field is set incorrectly in the Accounts Payable Open Invoice File.  Verify the invoice is not already selected for payment in another AP Data Entry Area such as Manual Check, Invoice Payment Selection, Check Maintenance, Invoice Data Entry.  There is a Sage Knowledgebase Article that explains how to clear this in v2021 and older with a Utility.  It also explains how to to do this manually in older versions. 

https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=18024&sliceId=1&isLoadPublishedVer=&docType=kc&docTypeID=DT_Article&stateId=3173&cmd=displayKC&dialogID=228614&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true 

Talked with Sage support. Apparently this is a known bug with older versions of Sage. You have to use Check and Electronic Payment Maintenance to bypass the bug. Essentially, we need to manually put a payment in the Check and Electronic Payment Maintenance screen. The manual payment option shows the correct balance.