At first I had the Sydney theme and even with this address it worked well. But now that I put other themes because I did not like it, the forum does not work anymore. The dates match it seems to me. First of all worked well, so I also put an old backup, but as soon as I wanted to change the forum it stopped working. Finally, I was advised to uninstall / reinstall the plugin, which I tried, and now the error is still different (I do not know if you had seen the previous one).

I am not qualified in the subject but I need this site, again I apologize for my english, and thank you.

I mean your permalink is no correct.

www.mysite.com/community/ is correct.

Your permalinks are ALL wrong.

http:// feeniks-minecraft.  myriapulse.  com /  index.php  /  dynmap/

http:// feeniks-minecraft.  myriapulse.com /  index.php / forum/

http:// feeniks-minecraft. myriapulse.com / index.php / messagerie/

...

I understood this, but HOW i can change the links ? And WHY my forum worked even if i had this links ?

Told you. Probably it is a problem with mod_rewrite.

But all these are beyond the scope of this forum and wpForo. Ask your hosting provider for more help, since you told us you are into technical details etc etc.