Have same problem here, last night wanna pump but kena declined, still got about RM70 balance left. Will try again later...

The cashier asked me to register and she gave me a registration form to fill in saying the card needs to be registered then only can use. But impossible that I can use the RM30 before registration and now RM70 left need to register to use it.  Hopefully ur info of 24hrs holding is true, that after 24 hours can use again.

I use fill up, cuz i always go for full tank. Later lunch time i will try again, i was informed about the registration last night when i get declined payment, today havent try yet.

I can use it already. Just bought some food in the Mesra store in the Maluri Petronas station. I think you're right about the 24 hours hold.
I think I know why is it.

Here's what I think why:
Ytd lunch time I bought a nasi lemak which was without a price tag using the pet gc in the same Petronas station, then the cashier used petrol to substitute the nasi lemak in the receipt in order to log it in the system. From then the credit started holding for deduction (usually within 24 hrs). Unfortunately the transaction was not successful as claimed by a senior staff there. He said that the nasi lemak credit deducted has been refunded in my pet gc. So which means i got a free nasi lemak ytd. Apparently it was a mistake made by a new staff in the station that he actually not supposed to allow non-price tag items to be used with pet gc as claimed by the senior staff.