Domain: https://www.amz2btc.com
Analysis from SSL Labs: https://www.ssllabs.com/ssltest/analyze.html?d=amz2btc.com
All my desktop browsers open this fine. Mob
A decent way to check whether there is an issue in your certificate chain is to use this website:
https://www.digicert.com/help/
Plug in your test URL and it will tell you what may be wrong. We had an issue with the same symptom as you, and our issue was diagnosed as being due to intermediate certificates.
SSL Certificate is not trusted
The certificate is not signed by a trusted authority (checking against Mozilla's root store). If you bought the certificate from a trusted authority, you probably just need to install one or more Intermediate certificates. Contact your certificate provider for assistance doing this for your server platform.