Are the running the latest solved plugin code? There was an update just over a week ago to fix support for Q&A structured data.
When I check random pages here on Meta, there are no Q&A page errors. If the topic is solved, Q&A shows no errors. If the topic is unsolved, it shows an error that there is no acceptedAnswer (as you’d expect). If the topic is in a category without solved enabled, Q&A type doesn’t show up in the structured data test.
Once you’ve confirmed that you’re fully up to date, if it’s still showing errors we’ll need to see one (or more) of the URLS giving errors so we can look into it.