I echo the others’ questions about why you aren’t using the built-in Let’s Encrypt support, rather than manually getting the cert and attempting to install it. But regardless of why you’re doing it this way, the error is telling you that the cert date is invalid, which is because it expired in April. You’ll need to either figure what you’re doing wrong in the manual cert installation, or figure out how to use the built-in automated support (with the latter being the better plan, IMO).