Cannot sign in to Microsoft teams – Error Code 80090026
We noticed that this issue started to happen on old Windows 10 machines, more exactly 1703 version. So, simply put, if your windows version is too old, you need to update your system. Microsoft did something with modern authentication on this version, so it does not longer work. Including Office Suite.
Anyway, here is the fix how to solve your issue:
Right-click “START” button, click on “RUN”, type: %APPDATA%
, press “OK”.
Navigate to “Microsoft”, find “Teams” folder and delete it. This will remove all cached stuff that made Teams stuck.
Go to Teams Page and download new Teams installation and install it.
And here where the biggest trick happens: In the Teams login prompt enter someone else (college’s or friend’s) e-mail address who has Microsoft account. Click “Sign in”.
Now, the new prompt window will pop up, click “Sign in with another account”. But this time enter your own login credentials.
Apparently, this “trick” helps to clean some “login stuff” off the client and let’s you sign in properly. It might show error on the first try, no worries, just close Teams and try it again (actually teams should restart automatically for you).
Hope it helped,
Audrius.