From your previous thread you used a --manual option to create your certs. As I noted then, you will need to continue doing that manually. If this is the only cert you will ever do and you plan to continue updating it manually you could disable the certbot timer.
But, if you want the renew to continue running you will need to add the ``--insecure``` option to your systemd certbot service profile for it. This is the same option you needed to issue your cert on your Arch Linux system. Until you resolve your root store problem this will always be needed.
That said, I am surprised certbot even made an attempt given the manual creation. You might want to review the conf file in the letsencrypt renewal folder. Perhaps it still reflects an attempt before using --manual