Try updating the firmware.
https://www.usa.canon.com/internet/...ips/battery-grip-bg-e22?tab=drivers_downloads
Firmware Version 1.0.1 incorporates the following fix:
1. In some cases the battery may not be charged through the BG-E22 when using the PD-E1 USB power adapter depending on the condition of the battery being used.
Firmware Version 1.0.1 is for battery grips with firmware Version 1.0.0. If the battery grip's firmware is already Version 1.0.1, it is not necessary to update the firmware.
https://www.usa.canon.com/internet/...ips/battery-grip-bg-e22?tab=drivers_downloads
Firmware Version 1.0.1 incorporates the following fix:
1. In some cases the battery may not be charged through the BG-E22 when using the PD-E1 USB power adapter depending on the condition of the battery being used.
Firmware Version 1.0.1 is for battery grips with firmware Version 1.0.0. If the battery grip's firmware is already Version 1.0.1, it is not necessary to update the firmware.
According to Canon, only genuine LP-E6N batteries will get charged in camera or in the grip.
https://shop.usa.canon.com/shop/en/catalog/battery-grip-bg-e22
See Comment below.
The LP-E6 will power the grip, but does it actually charge them? It didn't with the grip I rented, but that was almost a year ago.
I kept on looking after reading your comment, since I expected that there was something. I did find a product advisory stating it would not charge from the grip. I have several LP-E6 batteries, but didn't know specifically which are in the grip. I just checked and they are both the N version, so maybe the old one won't charge. In any event, here is what I found from 1.5 years ago before the firmware update.
https://support.usa.canon.com/kb/index?page=content&id=ART173597&cat=0901e024801101e8&actp=LIST
The charging is sometimes weird, When I checked just now, one was at 69%, the other at 98% and was not charging when I powered up the camera with my 3rd party PD charger. Pulling out the battery tray and reinserting it started it charging. I might try connecting the Canon power supply to see if it works differently. I think its out in my studio.
It does always get charged, but I don't think a battery should fall below 75% before it starts.