Failure to sign in

First of all, I have TEAMS on my old computer.  However, I bought a new computer, and I am unable to gain access to the TEAMS file on my new computer.

I gain access to TEAMS, it asks me to sign in again.  But the sign-up page does not open.  It ends there.  I have read the instructions and have spent over an hour trying everything without success.  It shouldn't be so difficult.