I activated ssl and everything was fine at first. A few days later, my website suddenly stopped opening, but I could still access the server.
I tried to reissue the certificate, but it didn't work. I exhausted my 5 attempts. Then I tried to delete it, but it still didn't work. What should I do?
Temporarily switch to a different CA like buypass or zerossl (or google). You will need to fix the "I tried to reissue the certificate, but it didn't work" because it sounds like it did work and that's why you hit the rate limit.
Check your domain is actually pointing at your server IP, currently it's a google server that's responding.
Requests to your domain get replied to by a google server. See: SSL Checker
You should review the IP address in your public DNS and make sure it points to your public IP and not google's server. If you did not set that up you should contact your hosting service.
Thank you! I followed your advice and was able to restore my work, but now I have a different question: how can I get the latest activated letsencrypt ssl certificate?
I don't see anything different. HTTP requests to your domain still fail. HTTPS requests still see a google server.
In your first post you deleted all of them. So, you will need to request another one. You were rate limited so need to wait 34 hours before a new request might work. See: Rate Limits - Let's Encrypt
An HTTP Challenge will not succeed until you fix HTTP connections. You never described what command or method you used to get the cert but a DNS Challenge might work even with your broken HTTP.