It sounds like this was originally an accounts payable invoice and check.  It's a matter of opinion, but I would have said the July General Ledger was off if it wasn't posted before it was closed and so I would have just re-ran July General Ledger.  Since that isn't what happened, I would say you should undo what you did and put things back to July along with the check that paid the invoice (don't mail out the check as the vendor was already paid), reclear the check, and rerun July General Ledger. The Financial Statements have a roll back feature if you need them.  You may have some reports outside of financial statements that you may not be able to roll back.   You can find many answers from Sage Desktop - Help - Sage Support - Knowledgebase.  See:  https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=49330&sliceId=1&isLoadPublishedVer=&docType=kc&docTypeID=DT_Article&stateId=8281&cmd=displayKC&dialogID=497906&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true

If you choose to leave this in August, you will need to issue a check in September (I'm assuming September because you say August CM is out of balance), not mail the check because you've already paid the vendor, rerun July & August bank recs, clear the check in September, and then I THINK you'll be back on track. - NOT SURE THIS WILL WORK. 

The Cash Management reconciliations may be out of balance due to the manual change you made to the "Cleared" or "Reconciled" status of the check in CM.  You should run the CM Report 'Bank Balance Verification".  If you find that one or more lines of that report for this specific bank account show variances, then follow the instructions in the Knowledgeable Article Solution ID: 25292. Variances in this report will impact bank reconciliation reports going forward until you make the corrections described in the KB article.