Welcome @marketingjarau
The "404" error means your system did not send the proper response to the Let's Encrypt Server.
When you request a cert your Cloudpanel should create a special token. It then asks the Let's Encrypt server to check that token and issue a certificate. The "404" means your system told the LE Server the token was "not found".
Something is not correctly configured in Cloudpanel or your nginx. You are probably better off asking for help at a Cloudpanel forum. They will know best how their system needs to be setup.
If you don't get any help from them you can come back here. But, we will want to see detailed logs from Cloudpanel and your nginx config.