By manually I assume that you’ve tried to upload the SSL certificate in the control panel, if so, does it show as uploaded but it does not appear on the site? Are you getting any error messages?
It should look like this:
By any chance, do you happen to be on any of the affected volumes (vol1_7 / vol1_8)? This could explain why you’re facing issues, as these volumes are currently being migrated to PHP 8.2.
I’m asking because the IP address your website is on (185.27.134.179) has been used for sites on vol1_8: