Means the mobile network randomly assigned an IP used for spam in the past (Probably cuz the spammer has the same mobile network)
It's actually really annoying when it happens, but it usually goes away after a while, otherwise you can try using a VPN if you really need to access gbatemp on your phone for whatever reason. When it happens to me I usually just give up checking temp notifications and try again another time. Usually goes away if you wait, and disconnecting from your network for a couple minutes sometimes jolts it into working, but not always.