I moved my dns from one clould flare account to the other cloud flare account. Clould flare informed me yesterday that the dns was moved successfully, and I started getting this error message :
Although Flexible mode works, it is not recommended to use Flexible as a long term solution - since your connection is not fully secure anyway (traffic between Cloudflare and your server is not encrypted). This will give users a false sense of security.
My suggestion is, get Cloudflare Origin Certificate installed in your server, then switch SSL mode to Full (strict) mode. It’s free.