Xbox Live & Possible Micosft Account Issue

I recently had to do a reset on my computer because it was having start up issues, and now when I try to log onto my Xbox Live (app on Windows 10; I'm using Version 1709, build 16299.309), I get this error message (without quotes, of course): "0x80070781 The name of the file cannot be resolved by the system." I can login and play as a guest, but not with my Microsoft account.

I have tried contacting both Windows and Xbox support, but neither seems to be able to figure out the problem. Can anyone help me find a solution to this pain-in-the-neck issue? It has been going on for almost 2 weeks.