Plan B: SSL works...kind of

I’ve managed to create an SSL cert with Cloudflare and import the cert to the mineos ssl certs folder (by SFTP) and then changed the 2 mineos.conf files (in /etc & /games/minecraft/) to use the 2 new crt and key files. If I use any of the SSL options on Cloudflare (flexible/full/strict) then I get an invalid SSL error when connecting on the 8443 port for MineOS. If I have it turned off on cloudflare then it connects to the mineos gui and says its secure, how on earth can it be secure but invalid at the same time?
I use Truenas aswell, and additionally cant get Truenas to work with that same domain:port on ssl.