So I have website hosted somewhere else on cpanel, and I want to migrate the website to another server with ispconfig but before migration, I want to host the website and test it. And letsencrypt is failing to create ssl, is it possible to create ssl even though website is hosted on another server and pointing to different NS and IP. I tried to add CAA record for letsencrypt, I tried to check on ispconfig server Skip Lets Encrypt Check. The only thing I can think of is copying cert from cpanel to ispconfig manually but I don't know if this is going to make any issues. Any suggestions?
LE certs require that LE is able to access this domain on the new server, that's impossible without pointing the domain to the new server in DNS first. So you can not use LE before you delegated the domain to the new server. What you can do is to create a self-signed SSL cert in this case. Or use an existing SSL key and cert from the system where the site is currently hosted at.
I think it may be possible if you use dns challenge, but it is not easy, plus your dns server must be supported and you really know how to do it. As confirmed by @till above, copying SSL certs should work, so do that as it is easier.
Yes, just copying the cert works, I manually input the cert from old server and it's ok now, I can work with it until DNS propagation and then I will generate cert on new server.