Yes, you may have an availability group – well done – and you may have installed SSRS on both servers. But you’ve only set up the reporting application to point to one of those? And you’ve given the link
https://<<Listener_Name>>/reportsout to the users? Head/desk. I told you at the time that SSRS doesn’t play nicely with AGs. [Nearly misposted as SSRS doesn’t play nicely with SSRS, which, while valid, isn’t the point here…]
Here’s what you need to do to fix this / make sure it doesn’t happen:
Click through to learn what you need to do to make sure there are no problems.