Why did my Beginning Balance change when I try to reconcile

Is your account set up for downloading the transactions?

If so, have you done anything that modified that connection, such as deactivate/reactivate, Reset, reauthorize, Add Account or Set Up Now?

If so, it is a known issue that sometimes this will cause the Opening Balance transaction dollar amount to be changed. A proactive step that can be taken (and is recommended): For all connected Spending accounts (i.e., checking, savings, credit cards, etc.) enter and save the Opening Balance transaction dollar amount into the Memo field of the transaction. This will not prevent the issue from occurring but it makes it very easy and fast to identify when it has occurred and to know how to fix it.

There is another issue that sometimes happens when modifying the connection method: Some duplicate transactions get entered into the Account Register. If there is an Account Register balance issue and if fixing the Opening Balance does not resolve it, you should scroll backward from the current date looking for duplicate transactions. If any are found, delete one of the transactions and retain the other. If this issue occurs, it is most likely that dupes will show up within the last 90 days.