The "404" in that error means "Not Found". The Let's Encrypt server made that HTTP challenge request to your server but your system said it was not found.
The --nginx option configures your local nginx system to reply to the LE HTTP Challenge. But, it looks like something other than nginx is replying.
If I do a curl to your domain I get redirected to an IP address that is different than what you have in your DNS for this domain
curl -i http://security.shishunir.com
HTTP/1.1 301 Moved Permanently
location: http://13.232.120.85
And, at that different IP an nginx system replies.
Can you explain what you are trying to accomplish? Because I don't think this exact configuration of DNS and servers will work as you expect
curl -i http://13.232.120.85/
HTTP/1.1 200 OK
Server: nginx/1.24.0 (Ubuntu)
Your DNS for your domain
nslookup security.shishunir.com
Address: 125.253.92.186