So says my new mobile provider and I've had a similar message on a WiFi network that I use sometimes.
Google tells me that this message means that "the site is claiming to be HTTPS-compliant, but either it’s not providing a certificate, or using an invalid one."
So my question is how secure is this site? It's one thing to be cautious about what you post in here but another one altogether if the site isn't secured properly.
https://www.fabguys.com/articles/FAQ
“We can access the site on Wifi but not on mobile network (or the other way round!). We get a connection/security/certificate error.
If you get a connection/security/certificate error accessing the site on 4G/mobile-data but not on WiFi (or, the other way round!) it means your mobile network (or ISP if on wifi) has blocked your device from adult content. Some mobile networks have started to do this to phones that have always been 18+ verified and some seemingly do it randomly. If you contact your mobile network on their helpline or via their website, you will see how to age verify your mobile account. The error you see is your ISP trying to display a message which does not show on a secure/ssl site like Fab. We've created a special page you can view which isn't served over secure/ssl so should be able to see the underlying message, here.
Once you have age verified your phone, your network usually advises turning the phone off then on again. It sometimes takes a few minutes then for the block to be removed.“
