My suggestion is as follows:
(1) Use SSL Labs to see what is wrong (
https://ssllabs.com/ssltest/analyze.html?d=yourdomain)
(2) make sure you have an SSL certificate (or use Cloudflare for a free one)
(3) force all your traffic to use https (cloudflare and other WAF/CDNs have this configuration)
(4) use Better Search / Replace and replace all the
http://yourdomain with
https://yourdomain
(5) clear all cache, CDNs etc.
(6) Test that all is ok using SSL Labs (
https://ssllabs.com/ssltest/analyze.html?d=yourdomain)
Also, if you are on a windows box, flush your DNS with "ipconfig /flushdns" command
If that doesn't resolve it, ping me and I'll take a look for you.