Site cannot be proven to be genuine

I am using an Android tablet and have tried this in both Chrome and Firefox.

I go to a site and I am given a message that my connection is not private and that the site cannot be certified as what it claims to be. It then says that this may mean that somebody is interfering with my connection with the aim of grabbing information. It also says thta it may be due to a misconfiguration.

However my trouble is that my Android phone does not display the same message on the same site. My PC and my wife’s devices also have no trouble. This leads me to fear that my tablet may well be comoormised.

Where to now, please?

Any help appreciated.

Does it only happen with one particular web site? If so which one?