I had some issues downloading the 2021 football tickets to my Android (Samsung S9) mobile wallet. However, I was able to solve the problem.
Steps to repro:
I attended the football games in 2020, and used the old version of Google Pay for the 2020 football season with no issues.
Recently, I upgraded to the new version of Google Pay (v134.1.2) on same Android phone I used during 2020 season. At the same time, I deleted the old Google Pay version.
I tried to transfer my 2021 tickets to my Android phone (with new GPay), but tickets would not show up in the new GPay.
I deleted the new GPay, and re-installed the old GPay (v2.134.389763251).
My football tickets/Champions Club passes suddenly appeared in the old GPay.
tldr; I successfully used old GPay during 2020 football season. The new GPay didn't work for loading 2021 tickets. I had to downgrade to old GPay to access my 2021 tickets.
DISCLAIMER: use this at your own risk.