Try acme.sh, it has an API for namecheap and can issue, install and automatically renew either zerossl (where the Issuing Authority is http://zerossl.crt.sectigo.com/ZeroSSLRSADomainSecureSiteCA.crt) or letsencrypt (Issuing authority is http://r3.i.lencr.org/) certs for free.
issue certs (just once)
acme.sh --issue -d yourdomain.com --dns dns_namecheap
Install certs (just once)
acme.sh -i --cert-file /etc/asterisk/keys/yourdomain.com.crt --key-file /etc/asterisk/keys/yourdomain.com.key --fullchain-file /etc/asterisk/keys/yourdomain.com.pem --reloadcmd "fwconsole cert --updateall;fwconsole reload; systemctl reload apache2" -d yourdomain.com
now you can remove your old cron job.
(If you are using another name service then
now has 136 other choices)