Our forum has worked fine for years and then suddenly disappeared, without any changes to the SMF. I finally figured out that the only thing that had changed was that I had updated the PHP on my server from 5.6 to 7.4. I went back and downgraded to 7.3, 7.2, 7.1, and finally back to 5.6 and that fixed it.
I apologize if this is answered elsewhere, but I can't find it. Why would it not work for the latest versions of PHP?
2.0.17 (officially) supports up to php 7.2, but it will log a lot of server errors. Will run fine in 7.1.
Versions before 2.0.15 will not work with 7.0
2.0.17 will work with 7.1, 7.2, 7.3
7.4 is not currently supported
I worked backward through the 7._ versions and the forum was still missing. My server provider's next choice was to go back to 5.6 and then it worked. Strange.
It sounds like you're still on 2.0.15. Have you actually updated the site to 2.0.17 yet?
Missing as in white screen or server error?
Just checked, 2.0.15 will load in php 7.0/7.1/7.2/7.3, logs a lot of errors above 7.1. Should not make forum "disappear". This sounds like a host issue.