Hey Romain, there could be a few different reasons.
The reason we recently added logging infrastructure to the plugin is to directly diagnose these kind of issues. We’ll be adding logging to the connection functionality soon, however it’s only currently active in the publication functionality.
A connection issue in the publication logs are unlikely to tell us anything useful. Nevertheless, you did mention an attempt to publish, so please first check the “Logs” admin panel in the WP Discourse plugin. You can share a specific line from the log, or share the whole log with me via PM. I’d also recommend issuing new API credentials in your Discourse and applying them in the plugin to ensure that’s not the cause.
Aside from that, while I wouldn’t want to turn this into a tit-for-tat with your hosts, an inability to cURL a domain, suggests an environmental issue, not a plugin issue. If you search for similar errors here you’ll find that @simon kindly helping various folks diagnose what are effectively environmental issues. For example (including some possible diagnostic tools) see
I’d recommend you press your hosting provider a bit more, asking them why there’d be an inability to make a cURL request to a domain. If they have some more specific reason to think it’s an issue with the WP Discourse plugin, and not say, an incorrect cURL version on the server (which on the face of it is more likely), they’re welcome to post here, or even pm me, and I’d be happy to look into it further with them.