Any idea what this means?

I moved into my flat at the weekend to discover it had a prepayment meter for electricity (flat only has electric supply no gas).

 Put £20 on the key and nothing happened, landlord has put £40 in total on the key friday & saturday, and letting agent has put £24 on the key (on Saturday which according to BG should have cleared any outstanding debt), agents have spent lots of time on the phone to BG, to no avail!

Flat is uninhabitable as there is no light, heating, or hot water, BG are supposed to be coming Thurs PM but I'd like to know what the error means and if a new key which is meant to be in the post will solve the issue

 TIA