Hello Colourqueen and welcome to the eForum
The 635 error is one of the more vague codes, but primarily revolve around being able to make an internet connection.
Please could you try a few tests as follows:
1. Put the Vodafone sim in a phone and try to connect to network.
2. Try to use the built in Modem if you were aware of it, the sim slot is located behind the battery.
Thanks
Reidar
eForum Team