IU error

I was driving out of the Sheraton Towers car park last evening and it took a while for the system to deduct the fee from my In-Vehicle Unit (IU). [To those not from Singapore, this is a device used in our Electronic Road Pricing which is installed in vehicles so that money can be deducted when entering town during busy periods.]
Finally, when the amount was deducted, the IU made a loud, high-pitched beeping sound and displayed the word ‘Error’. There was an icon that looked like an empty battery.
Checking the One Motoring website, it appears that I have to send it to a service centre for repairs. Argh. My schedule is full this week, how to make time to go for servicing??
And I hope I can get into the office car park this morning, despite a wonky IU – I’m a season parker.