Now, before you perform this process, I do advise that you Save a Backup. (You can do this by navigating to File and then Save a Backup.)
Note: Pay special attention to the Action column when your account pulls up to make sure that that you link it to your original account (the one with the full history) instead of ADD, otherwise you’ll end up with duplicate accounts again.
Your account(s) should perform an update, pulling in missed transactions and bringing you up to date. The same process can be applied to the credit card accounts that you mentioned in your last message as well.
Lastly, I would advise you clean up your register by disposing of those extra accounts. You can go about this in one of two ways - by deleting them or by keeping them hidden and separate.
If you decide to delete, I would double check to make sure there is no information in these accounts that you don't already have in other accounts as this is permanent and you will lose this data for good (unless you restore from a backup). You may do this by navigating to Accounts and selecting Delete Account... or by Right-Clicking/Command-Clicking the account and selecting Delete "Account Name"
If you would rather not delete, you may navigate to Accounts and then select Hide and Show Accounts. From here you may check the boxes next to the specified accounts to mark them as hidden and/or separate.
This should get you back to normal. If you require any further assistance or you have more questions, please get back to us so that we may assist you further. Thank you!
-Quicken September