Mydomain.netai.net unsafe warning!

as the above image…how to fix the netai.net unsafe warning issue??

You can’t use “https” for free subdomain…like “netai.net”.
But you can use “https” for *.000webhostapp.com domain names.(because of shared ssl)

or grab a free domain from (freenom.com) and use cloudflare for ssl.

Hope this makes you clear.

Can I use a free SSL certificate on a freenom.com free domain?

@LeonLaci Yes you can.
Check this tutorial,

It means that if I pay to become a platinum member, still can’t use "https: for .netai.net ??

if I still need to use mydomainname.netai.net… how can I reach it?

There is NO option for HTTPS on free subdomains from 000webhost.com

There is FREE HTTPS on 000webhostapp domains.

There is FREE HTTPS via CloudFlare and free domains from elsewhere like FreeNom.com

There is no sense in having HTTPS on a free subdomain from 000webhost - you will never own the free subdomain and it may be taken out of service at any time.
Just do not use HTTPS - use plain old HTTP.