I tried endlessly for over half got before I got tickets. I got error messages through every stage and lost out on so many good seats but eventually got half decent tickets!
It worked on my phone rather than computer.
And I found it helped to already have an account set up with your address and card details added.
When I tried to enter them at check out I kept getting errors so I added all the info separately onto my account and then it worked when I went to search for tickets again!
I’m from U.K. And had to choose e-tickets
Good luck!