Thanks
Does the problem only occur on the registration page or does it affect the entire site?
You can try accessing the registration directly using this URL: https://megapari.com/registration.
Anyway, I didn't notice any errors, it's possible that the issue has already been resolved. Also, since you're using Linux, it's possible that the certificate issue only impact Linux machines.
But be careful with this site. It appears that they are affiliated with the 1xBET parent company, which has a bit of a reputation in the gambling community for being involved in some pretty shady practices and selective scamming. If you ever face any issues and the casino decides to confiscate your funds, don't expect much help or an explanation from their customer support or security department. So, be cautious if you decide to engage with them.