Profile Installation Failed. A SSL error has occured and a secure connection to the server cannot be made.

Before the Covid shutdown at my college I was trying to enroll new iMacs to our Mac Server via Profile Manager and when I hit enroll I would get the error...

Profile Installation Failed. A SSL error has occured and a secure connection to the server cannot be made.

So I thought we needed a secure certificate and i ordered one. Since then I haven't been working on these machines and today I loaded the certificate via the Mac Server and it's authenticated.

When I tried to enroll devices today I am getting the same error.

I can find no explanation online and honestly i'm starting to panic. Can anyone assist please?