To use the wildcard SSL certificate Gazella need to set up on our server where sys.gazellawifi.com is hosted. But this is not the right way because cert files (especially cert key) should not be shared with anyone due to security reasons.
We think a suitable solution can be to use Cloudflare service. They need to move their DNS configuration to Cloudflare where they are able to set up a CNAME record as an alias to "sys.gazellawifi.com" and enable traffic redirection to "your URL" through Cloudflare servers.
In this case, it will be using the certificate of Cloudflare service, not their wildcard certificate, but however, the https secure connection will be enabled.