Electric key error

I am new to bulb. I was told to use up my old credit, insert my bulb key for 60 seconds then I can top up using my bulb key. I have done all that this evening but my bulb key comes up with error4! So I can’t put my credit on and have little credit left on the meter, I’ve tried calling bulb but they’re closed so I don’t know what to do

I’m just another customer, does this Bulb page provide any help: Top up meter error codes and messages – Bulb