Since a while, I often have problems to charge my FP1.
I need to switch off, remove the battery and re-plug it, and finally, after a restart, my FP1 can charge again.
During the day, if I unplugged the cable and re-plugged it, it will charging again.
But you can be sure than on the 48 next hours the charge will stop again !
Also check the charging port for dust. In my own experience (your mileage may vary), removing the (compacted) dust and fluff from the connector reduced the occurrence of the problem. I used a sowing needle as compressed air wasn’t doing the trick; be careful not to damage anything if you try this.
The problem completely disappeared when I bought a new a battery, but the cleaning already significantly improved matters.