CNAME and using the forum as a sub-domain

[Da G]

My domain is disidencia.info

I've had my forum running as www.disidencia.info for 2 years now, minor issues, no complaints. I'll renew the subscription for one more year within 5 days

Now I want to have the forum running as a feature for my website, currently under constructuion, so I have to set it up as a sub domain. It will be forum.disidencia.info

I created this CNAME entry

forum

0826afe3-8347-403a-a309-d3543629a0fe.vbulletin.net

14400

I'm aware it is said that it should be blahblablah.vubulletin.net. but my zone editor doesn't allow it, so it has to be with the final dot missing

Now if I ping forum.disidencia.info it's translated to

Danis-MacBook-Pro:~ Dani$ ping forum.disidencia.info
PING d3543629a0fe-000703.vbulletin.net (98.158.199.20): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2

So it looks right for my stupid and illiterate eyes, DNS translates it...but it doesn't work, so it cannot be right

At the very same time, my forum which you can visit here, https://d3543629a0fe-000703.vbulletin.net, doesn't apply CSS

What should I do?

Thanx in advance

[Mark.B]

Duplicate.