Authentication rejected

I run Teanviewer to support my clients and this works great. I also use it to log into my office  desktop while I am out of town. This also worksgreat - for about a week - then I get Authentication Rejected and I cannot log in. When I get back to the office I cannot see anything on the desktop computer that indicates why it stopped authenticating. I take out the laptop that I travel with, load Teamviewer and log into the desktop, no problem. This has happened several times over the last year. (every time I leave for more than a week). Can anyone shed some light? Any advice would be greatly appreciated.