I thought it might be a local network problem, but I also use admin from my mobile, and I get the same error using LTE or wireless networks outside of home. I have been using private browsing and clearing cache often does help sometimes, but only temporarily.

This is the page I get now. I've checked the error log but it's empty.

Hi  jasonb,

We've just checked your website and didn't find this warning. Probably some action was made on the server side, so you found this warning. We cannot guess what's gone wrong as we couldn't find it.

Hi Sofy,

Thanks for looking into it. I worked with siteground chat support and we created a new admin user. The problem was resolved. Something has corrupted my original user, but it's not a wpforo problem. I think it's related to having bbpress installed before. I'll get with them or use this workaround.