It most likely has to do with certificates being expired / invalid (possible MITM attack). Possible concern if one is sending credit card info or is using same id/pw on sh as other places.
Highest probability is hosting service has not updated certificate info.
You are 98% probably correct about certs being expired.
You are 10% probably correct about Man In The Middle attack. Saddlehunter is not a HVT. Besides the store (Paypal) not much finance-related happens here, unless individual users are super super dumb.
This MITM stuff is good reason to NEVER use the same id/pw on multiple sites. The risk is low, you're 100% correct on this.
@Dewey next time please click on "Details" when you screenshot these kind of errors. The way companies wrap up technical problems inside fluffy "this website may be blah blah blah" is kind of useless for getting to the bottom of things.