Sometimes happen that you are already logged into some Sharepoint site via browser credentials (ex.: via domain credentials),
but accessing particular site gives you ‘Unauthorized’ or ‘Sorry …’ result – logged account hasn’t access to this particular site.
Even if you know valid credentials to this site – you just can’t simply log out (sign out) and log in (sign in) with proper credentials!
Simple solution is : enter below url (add it to site url) :
[site url] /_layouts/closeConnection.aspx?loginasanotheruser=true
some example url will look like :
Credit goes to Kuba 🙂 .