TLS cannot be trusted


I use Cloudflare to have a secure SSL but as I know from some countries like Romania, it says that the TLS cannot be trusted. I use the FULL SSL certificate because I have subdomains connected to my main domain too.
my main domain is
my subdomain that I am talking about is

Which type of SSL should I use?

P.S: Here is a screenshot of that from romania:


The Cloudflare certs can only cover *, (i.e. but not *. *, (i.e. You either need to set up that subdomain without www or buy a dedicated certificate and add that hostname.