Error 520 Web server return unknown error

I am having 520 error on my site when enable cloudflare:
Cloudflare Ray ID: 676764108b9053f8

uag=Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.107 Safari/537.36

Regarding 520 error, may I ask have you checked withinh the below article(s)?:

May you check with your hosting provider and at your server firewall, if Cloudflare is allowed to connect to your origin/host?

Cloudflare IPv4 & IPv6 ranges can be found here:

Currently, I am getting SSL_ERROR_INTERNAL_ERROR_ALERT when trying to open your website over HTTPS on FireFox, while ERR_SSL_PROTOCOL_ERROR on Chrome.

Seems to me we cannot establish an HTTPS connection either due to not having an SSL certificate found on, neither possible it works over a non-compatible port like 443?

It works on HTTP currently.

Does your server run over HTTP or HTTPS?

Furthermore, regarding SSL, have you had an SSL certificate before moving your domain/website to Cloudflare?
If yes, is it a valid SSL certificate, which covers both your main domain and your sub-domains too like and

Which SSL mode have you got enabled (Full SSL, …) at SSL/TLS tab on Cloudflare dashboard?

About available options at Cloudflare dashboard → SSL/TLS tab, check here:

Kindly, check the instructions from below article how to propperly setup the SSL and how to make sure you have the right SSL setup using Cloudflare for your domain:

Useful tips to check out too:

In case you do not have an SSL certificate, you can also generate a Cloudflare Origin CA Certificate and install it at your host origin/server, switch to :orange: cloud and select Full (Strict) SSL:

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