I got 526 error when trying to visit your Website. May I ask what steps for troubleshooting have you tried already related to the 526 error you’re experiencing?
Might be the connection between Cloudflare and your server detected some issue such as the SSL certificate at your origin host/server for your domain expired, therefrom Cloudflare tries to establish a connection over HTTPS and 443 port, but cannot.
Possibly, if you’ve left SSL/TLS on “Automatic”; it might detect and switched to Flexible but now you might be experiencing issues such as mixed content errors and cannot determine how to proceed further.
Otherwise, it switched to Full (not strict) to still have room so your origin Let’s Encrypt SSL certificate could still try to validate and renew (if Always Use HTTPS is disabled).
Have you checekd your CF dashboard under the SSL/TLS settings, did it switched to Flexible or not?
May I ask what SSL option have you got selected under the SSL/TLS tab at Cloudflare dashboard for your domain ( Flexible, Full, Full Strict … )?
Before moving to Cloudflare, was your Website working over HTTPS connection?
Best way is to temporary Pause Cloudflare for your site. Wait few minutes. Double-check the origin SSL certificate. Renew it. After the Website works okay over HTTPS, un-pause and all good.
Steps for troubleshooting:
Use the “Pause Cloudflare on Site” option from the Overview tab for your domain at dash.cloudflare.com .
The link is in the lower right corner of that page.
Give it five minutes to take effect, then make sure site is working as expected with HTTPS without any error
Check with your hosting provider / Plesk panel / cPanel AutoSSL / Let’s Encrypt / ACME / Certbot and manually click to renew it
Only then, when your website responds over HTTPS, you should un-pause Cloudflare and double-check your SSL/TLS setting to make sure it’s set to Full (Strict).