I'm not sure if it charges while in bootloader (not hboot), but leave it connected for a few hours and try again. I don't think that's your problem though. Have you tried just rebooting the PC? Or tried on another PC?
Sent from my Evita
OnePlus One | crDroid/AK | TWRP 18.104.22.168
Do not PM me asking for assistance, that's what my Q&A thread is for!