Trying to book a flight on the AA website. It gives me all the options, I choose the flights I want, I get to the "Your Trip Summary" page, press to proceed and always get taken back to the beginning with the following error message:

Choose a different flight or fare

We're sorry but at least one of the flights or fares you chose is no longer available


But then all the same options come up, and all of them take me back to this message like a continuos loop.
Is there a workaround for this? Thanks for any help.