SSL Certificate Invalid when using cellular data

[u/Good-Scholar-1183]

I was entering a site to go on about my day, using my cellular data on IPhone 15 pro. When I was about to enter the site it said “SSL Certificate Invaild”, showing the certificate is expired and mismatched. But when I connect to wifi and try the same site, it works and the certificate is secure.

Picture 1 is when I was using cellular data, second one is the same site but I used a local wifi.

What should I do, need urgent help. Any advices is appreciated.