Proochles
I have found the following error in your forum logs on the server side:
flarum.ERROR: Swift_TransportException: Connection could not be established with host smtp.<xxx>.tech :stream_socket_client(): php_network_getaddresses: getaddrinfo failed: Name or service not known in /app/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Transport/StreamBuffer.php:261
This is probably not related to Asirem (but your SMTP settings, or server), however it might explain why your forum didn't function the way it should. You can view all of your logs at https://freeflarum.com/settings/logs, BTW.
The Asirem error has to be reported to the extension's author. We can't fix bugs in extensions, as we're just hosting provider. My best guess is that it might require some additional extension to be enabled, otherwise it crashes the forum. If you want, I can create a temporary admin account at your forum and grab the information needed in order to report the issue.
Equinemarkt It was related to katosdev/signature, since disabling that extension fixed the issue. Because I knew the exact error message, I've reported it to the author here