iPad Pro "Not Charging"?

Recently bought a iPad Pro 9.7" in like-new, open box from a very reputable seller (based on the amount that was sold and their high feedback rating) online and for some reason, I am encountering a "Not Charging" problem. I am using the 12W power brick that is included, it appears to be new in its plastic wrapping.

I've tried the following in an attempt to figure out the issue:

- Using different Lightning Cables, did not work

- Using the reverse side of the Lightning Cable, did not work

- Using the iPhone power brick, did not work

- Plugging into different power outlets, did not work

- Unplugging all other chargers surrounding the outlet, did not work

- Plugging into a Portable Charger, did not work

- Restarting the device, did not work

However, one thing I've noticed is that when the charging does work, after a while it will stop charging and show the Not Charging issue.

Currently running on 11.2.2, if this info helps. As of right now, I am charging my iPhone on the same outlet shared with the iPad Pro and the iPhone is charging fine as usual with no problem.

Any help would be appreciated, cheers.