take a look at my two posts here, they cover everything you need to convert to https, they'll cover a bit more than Justins excellent video, so do please verify you didn't miss anything
How can I configure System Center Configuration Manager in HTTPS mode (PKI) - Part 1
How can I configure System Center Configuration Manager in HTTPS mode (PKI) - Part 2
also, keep in mind that certs can expire, and when they do you'll have issues, like this
https://www.niallbrady.com/2020/08/16/how-can-i-replace-an-expired-iis-certificate-in-a-pki-enabled-configmgr-environment/
if you want to really test PKI is working then try pxe boot (operating system deployment), if it fails you'll see it failing quickly in the logs, and that'll be a clue that you've missed something,
also, on PKI managed clients, your configmgr client agent should report that the client is PKI, like this...