Does Firefox show that you have any add-ons installed right now (not searching for new ones)?

Can you think of any apps you installed recently that might have changed how your other apps connect to the web?

Does this affect mobile networks or only wi-fi?

About that last question: Android allows proxy servers for wi-fi connections. In order to reach HTTPS addresses, proxy servers need to provide a fake site certificate to the requesting app, and Firefox typically would reject that unless/until set up to work with the proxy. I'm not sure how to investigate whether this might be the issue, but you could check your wi-fi "advanced" settings.

addons are Tap translate 0.3.6 and OpenhH64 video codec from Cisco. The phone is not currently used as a cell phone (no plan).

We have a number of other PC's on this wifi network non of which have issues.

The wifi advanced settings are basic on the phone.

Network notification when open networks are within range and Always allow scanning

no new apps downloaded recently

Bryan

Does Firefox have the same problem in a Guest session? That seems to bypass most customizations, so would be a less drastic test than deleting all your Firefox Data.

See: Share your Android device with a Firefox Guest Session

The galaxy grand prime doesn't seem to have a guest mode???

It should be on Firefox's Tools menu a couple slots down from Add-ons. No?? I don't know why that would be missing.

From what I can tell, the guest session feature dates back to Firefox 25.0 for Android. What version are you running now?

I found the problem but I thought you might be interested in the solution.

The phone date had been reset to Jan 2015. I can see from the last sych date of gmail that this occurred on the 28 th Oct.

The mystery now is how that occurred, I certainly didn't do it, and it doesn't look like a global reset to factory defaults???

Thanks for your help

Bryan