I still say it would of been more likely internal dns having issues. I've had my own NAS do same thing it came down simply clearing stale dns records firstly by disabling the lan port pc then enable and then flushing dns several times and then repeat disable and enable of lan port. This trick fix my own NAS. But other point as  I tried to highlight at start was to make sure you using correct login details . Seems what I said didn't get done at start as you wouldn't of need anyone to use team viewer if you actually did as I said. Hense why didn't bother doing any further posting as I could see I was wasting my time explaining