It got resetted because of the update. Try "admin" as username and password to log in and then simply change it in the settings.

It worked! Thanks a lot.

Hello, I have a TL-WR841N v8.4 router. Current firmware is 3.15.9 Build 140724 Rel.63227n Now I checked the firmware page and when I chose V8, there appears to be a new firmware version called...