I had the same problem, and what did the trick for me was to put a check mark in the box that says do not store password.  

I would also recommend that you go to the task scheduler, delete all QuickBooks Company backups that are already scheduled, then go back to your company and set the backup from scratch.  (In other words delete any previous schedule backups, then re-schedule, go to task scheduler change to windows 10 and put a check box to not save password.)  Mine have been working ever since.

Hope this helps you!