Error : Not find the user in chrome

I get the following error when surfing in chrome and/or lightning : Not find the user.
I only get this message when WIFI is not available and not all the time.
Has anybody the same issue or can anybody help me?

Many thanks in advance

I entered the APN settings from my provider manually and now it seems to be working fine!
So if anyone having the same issue try this first!
Kind regards