I can see that you did everything you could, @PowPow. I'm here to share some details about this. 

The issue of getting an error when accessing Merchant Service Deposits in QuickBooks Desktop (QBDT) is still ongoing. Currently, we don't have an estimated time frame on when this will be resolved. If your account was already added to the list of affected users, you'll receive updates about this via email.

The recommended workaround for this is to locate all places you've added backslashes and manually remove them. 

Please know that you can always post here in the Community if you have any other QuickBooks concerns. I'm always here ready to help. Have a good one.