Please allow your headset sit for up to 48-hours unplugged to allow the battery to drain before moving onto the hardware reset.
Check to make sure the USB port you are using is supplying enough power to charge the headset and that the charging cable is not damaged. Make sure both the cable and charging port are free of debris.
The best way to do this is to attempt to charge a different device, such as a phone, using the same cable and port.
Once you confirm the cable and port to work, plug in the headset and perform a reset
The same steps will work for all Arctis 7 models, including 7+, 7P, 7P+, 7X and 7X+
Arctis 7
There is a hardware reset switch under the cushion on the left ear cup (side with the mic). It is a pinhole so it will require a paperclip or pin to press. Press it and hold it down for ~1 second.
If the headset continues to not charge, please click the chat icon in the bottom-right corner to contact our Support team.
Here's a video on how to perform the steps above: