Question about Panasonic RF-D30BT

Justified question!
I put in 4 freshly charged HR14 Baby (C) battery NiMH 4800 mAh today and I can't get the thing to work. It won't turn on. :-(

If I insert normal batteries, it works. I can't find any indication in the manual that it won't work with rechargeable batteries. It mentions the following:
Power supply: Battery DC 6 V (4xR14/LR14)

Does anyone operate this unit with rechargeable batteries?

I'm sorry, I can't answer that.
Greetings