when I tried to install SSL private key it shows “The private key you are trying to upload is not valid.”
and when I tried to install the SSL certificate it shows “The certificate uploaded is NOT for the domain name clustus.live ( was seen) .”
Last time someone reported an issue like this, it turned out that their browser or device was manipulating the clipboard contents and adding junk data to it. And the panel will refuse the key and certificate data if that junk content is added.
I would definitely suggest trying a different browser on a different device to rule out this issue.