Unable to join a hosting friend, but when the aforementioned friend tries to join me, when I'm hosting, it's "as smooth as butter"

As stated above, I can host without any problem (except for the fact, that my FPS goes to shit whenever I host), but when my friend tries to host, I can't join him at all
Both of us are using the same versions of the game, although his game is off of steam and mine is outside of steam, so we play over Hamachi, by connecting over IP
Both of us have both Hamachi and the game allowed in our firewalls, both of us don't f*ck up the IPv4 and Port when hosting/joining, both of us set the delay at 200ms even if our delay is just a mere 30ms

We have genuinely no idea on how to make the connection work

Check if the game is allowed in firewall on his end - that sounds like the only thing that could go wrong here.

"Both of us have both Hamachi and the game allowed in our firewalls"

We even re-checked, and they are allowed in both of our firewalls

So we basically have no way to make him host and also have to suffer through my fps?