I was having the same issue/same error and just got it resolved. Here's what happened for me (not sure if it will be applicable to you):

- Booked via JAL with AA and JAL metal in the itinerary (AA -> JAL -> JAL -> AA)
- One AA flight had a schedule change. I was seeing that timeout error when trying to access my booking to confirm the schedule change on desktop and the mobile app.
- I called customer service and confirmed/accepted the schedule change
- I was able to see my booking again after accepting the change with a CS agent

It was a bit of a clunky process, but hopefully that can provide some useful info for you.