DO NOT UPDATE BIOS TO VERSION 1.17.0

Your post is meaningless because you neglected to specify which computer model the BIOS caused the issue. 

@Chino de Oro​ G16 7630. I'm guessing this has affected a lot of people as they just released 1.18.0 today, 2 days after 1.17.0. Unfortunately it still hasn't fixed the problem.

Your post becomes more helpful when including the system model of G16 7630.

You may be right about the BIOS issue as the new release was pushed out too soon.  Have you try to perform a reset to see if it could fix the problem?  Remove power from your system, remove or disconnect the battery.   Press and hold the power button for 30 seconds.  Connecting all power and check again.

I wonder why support did not offer a BIOS bridge firmware to help you downgrade to previous BIOS version.  Just post the update progress of the new motherboard if you will.

Not sure when I'll get the new board cause now they're telling me it's delayed because there are no parts available. One benefit I did see from the new BIOS is that it reduced fan noise; unfortunately at the expense of greatly decreasing performance. Hope they get the replacement board soon or come up with another BIOS update to fix the problem cause I'm just outside the return window at this point and stuck with this garbage.

Don't let your hope up.  If your BIOS firmware update has changed some parameter and causing AC adapter not being recognized, a new motherboard may or may not resolve the issue of recognizing the AC adapter.  I would of testing with a different firmware, a different charger, or move up to 330w charger if currently use 240w.

@Chino de Oro​ Unfortunately BIOS Guard prevents downgrading even when the downgrade option is enabled in BIOS. You'll just get a message that the update is blocked due to unsupported downgrade. And the adapter that came with the laptop is already 330w.

I only threw some idea out there.  You already tested with different firmware, 1.18.0.  It did not fix the issue, therefore, the issue was not cause by the BIOS firmware 1.17.0.  I also suggest to test with a different charger.  

Do you know the reason why Dell support wanted to change motherboard.  Maybe you can wait for the motherboard replacement and post back if it does not fix the issue. 

@Chino de Oro​ whatever they did in 1.18.0 didn't fix the issue caused by 1.17.0 but 1.17.0 definitely broke it.

The agent asked me to run Dell's log collector and after reviewing the results concluded a motherboard replacement. I'll update the post if/when the board gets replaced but I'm going to first try asking to either return for a refund or a replacement with 1.15.1. Who knows when they'll have the part when a brand new one can be built and shipped in just a few days.

In my experience, the error of unknown AC power adapter was usually caused by a worn out or damage of the center pin on the AC adapter connector tip.  It could not confirm to BIOS firmware that a genuine and supported AC adapter being used.  Hence the error message. 

While the actual power from AC adapter still works and is able to power the device (laptop), the BIOS firmware blocked it from full performance (CPU downclocked) and prevent charging function (the battery).

That was the reason I doubt the action taken by motherboard replacement can resolve the issue.  You can only request a return for refund if you are within the eligibility return window.  If you do not want to wait to find out, test with a different AC adapter to see if it can fix the issue.  Remember to perform a hardware reset by removing AC power, and battery from your laptop.  Press and hold power button for 30 seconds.  Connect the new AC adapter for testing.

AC adapter is covered under warranty if it failed electrically due to factory defects.  If the center pin was broken off or damaged due to usage, it will not be covered by warranty.  Of course, this is my own opinion based on reviewing Dell policy.  A warranty claim is certainly still needed and hope for a better outcome.