In my own personal experience, if http is working, but httpS isn’t, the system often just has a problem with SSL.
If the shell of the system has wget or curl, you can try just accessing an https url to make sure you get valid data.
Maybe just ‘wget https://google.com’ or 'wget https://GitHub.com’
If one site works, try accessing your https feed urls with it to make sure they also work.
By no means exhaustive, but the most common solutions for me have been:
- Make sure the date and time are set and correct, within a few hours at least.
- Update CA Certificates. This can sometimes be done with a package manager or normal update process, but some systems you have to update this manually.
- Most recently, a hard requirement of a CentOS5 system meant I also had to compile a new OpenSSL and wget, and update cacerts manually to access directly. Supporting extended LTS stuff sucks sometimes.