I moved your reply from the Simpsons Tapped Out to SWGoH:bugs and issues.
I think you be better helped here.
I had the same issue, and I even contacted the EA tech support to see if they could resolve it. No luck.
Then I found a solution online that worked.
For iOS users, go to Settings>General>Reset>Reset Network Settings. This will reboot your device and erase your WiFi passwords, so you will have to key them in again after your device restarts.
I realized that the game gets stuck at the 'Loading Cantina' screen because it is unable to access and connect to the Game Center. I think Star Wars: Galaxy of Heroes is a game that is dependent on the Game Center for storing achievements and other player data. By resetting your network settings, I believe it repairs the connection between the game and the Game Center.
I will share this on other forums to help others who are facing the same problem.
Note: The above steps are for iOS users. I am uncertain if Android users have the same log-in problem.