May I ask have you recently:
- Added your domain to your Cloudflare account?
- Changed the nameservers to Cloudflare one’s for your domain name at your domain registar?
- Waited for some time due to proper DNS propagation?
- What is your domain name?
Regarding error 525, it should have to be something with SSL certificate at your host/origin and Cloudflare SSL options. Kindly see here:
Seems to me you did not have had an SSL certificate installed at your host/origin server before moving to Cloudflare?
Moreover, if you have had it, maybe you have wrongly selected/setup the SSL settings at Cloudflare dashboard.
If so, kindly re-check with the suggestions from the below article how to properly setup the SSL with Cloudflare:
Helpful article about SSL settings available at Cloudflare:
To troubleshoot, check here: