Wondering if anyone else has this problem and if they can offer a solution ...
I have a Lumia 920 running on the Vodafone NZ network, with a data plan.  I was happily using Internet Sharing a couple of months ago without issues.  Today I went to use it and I am no longer able to turn Internet Sharing on - I get the message:
"Connection not shared.  There's no mobile data connection to share at the moment.  Check your mobile settings and signal, and try again".
My dataplan is active and working.  I have not changed plans or anything else recently - I can only think that the Amber update I got a couple of months back may have affected this - I haven't used the internet sharing since the update.
I tried one of the internet suggestions of creating a dummy APN via Access Point and soft re-starting etc to re-connect the data, but this did not change anything.
My phone was purchased unlocked from Australia:
Phone Details:
Manufacturer Name: RM-821_apac_australia_new_zealand_304
Mobile Operator: 000-AU
OS version: 8.0.10328.78
Carrier: Australia
Firmware version: 3049.0000.1330.0006
Access Point: Version 3.8.0.6

Apologies if this is in the wrong forum.  And Thanks in advance ....