Are you receiving an error message when attempting this? Please let me know if you did and what the error message stated.
Have you tried completing this using a different browser? Have you also tried clearing the cache on your PC?
I just logged into my own Backup Assistant and the system did allow me to get to the right page. Are you using the username and password of the mobile number you are trying to access? Please note that the username and password for the number you are trying to view is the same as the My Verizon username and password this same number uses.
Please let us know if you need additional assistance. Thank you!