Is this very normal if it is in the propagation stage?

Hi. Is it normal if I just moved the domain name server to CF, then deleted SSL Lets Encrypt in the terminal and suddenly the website went down 521

is this very normal if it is in the propagation stage?

Did you delete the SSL certificate on your origin? That was the wrong thing to do. Cloudflare will use that to connect and secure to your origin even though visitors to your site will see the Cloudflare edge certificate.

Put the certificate back and ensure your SSL/TLS settings are set to “Full (strict)” here…
https://dash.cloudflare.com/?to=/:account/:zone/ssl-tls

Otherwise, if still stuck, what is the domain name?

Not ssl cloudflare. im just delete ssl certificate certbot

Yes, that’s what I meant. If you deleted the SSL certificate on your server that was the wrong thing to do. You need an SSL certificate on your origin to allow Cloudflare to securely connect to your server.

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then when I wanted to install certbot again, an error like this appeared. is there a solution? or is it just waiting for propagation to complete and then installing certbot?

You have not set Cloudflare nameservers at your registrar yet (or your registrar hasn’t processed the change).
https://cf.sjr.org.uk/tools/check?b501cf37fefe4684afb28d79da0edc84#whois

Go to the bottom of this page, there will be two nameservers of the form name.ns.cloudflare.com that you need to set at your registrar.

As your domain is not added to Cloudflare yet, your certbot run isn’t affected by Cloudflare so you will need to debug that yourself.

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Because I was worried that propagation wouldn’t be finished until the next few minutes, I changed the name server to default again and reset the moving date to Cloudflare. Did the error occur because my domain was in the process of propagation so I couldn’t install Certbot? After propagation is complete, can I install it normally?

Get your server working with SSL first so you know everything is operating correctly BEFORE adding to Cloudflare otherwise it gets very hard to debug. Do one step at a time.

Once your origin server is working correctly, then you can change the nameservers to Cloudflare. When done, post back.

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OK, I understand that problem. Thank you very much. but please add one additional case regarding the SSL installation error, is it because the propagation process is still running?

Maybe, but LetsEncrypt goes to the root servers for DNS so if updated by your registrar, it should work. The checker link I gave above also looks at the root servers so if those are the correct records, propagation isn’t an issue.

Looking at those, it seems you have some extra nameservers set that shouldn’t be there. Seems you have added 3 NS records to your DNS.

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all three are the ns domain providers I bought

You must replace them with the pair assigned by Cloudflare of you want to use Cloudflare.