Latitude 5480 and WD15

I think the above AC adapter issue will be the culprit, but since you mentioned a BIOS update, while there's no "BIOS" update for the WD15, there's a firmware update for the docking station if you go to support.dell.com, click "Select from all products" and then go to Accessories > Docks > WD15 > Drivers & Downloads.

Read through these two articles to verify that some troubleshooting was not missed =
How to Use and Troubleshoot the WD15
WD15 User's Guide

Check the WD15 drivers page.

What is the wattage of the AC adapter you've got plugged into the WD15?  To use the WD15 with the Latitude 5480, it needs at least a 180W adapter connected, and the WD15 is sold with either 130W or 180W adapters depending on the system(s) that you may need to use with it. You CANNOT just use the AC adapter that comes with the laptop to power the WD15, since that will not be enough total power to run the WD15's internal electronics AND send to the laptop itself over USB-C. This wattage requirement (as well as a lot of other useful information) is explained here: https://www.dell.com/support/article/tr/tr/trdhs1/sln304627/dell-dock-wd15--usb-type-c---information--capability-and-specifications?lang=en

The adapter is 180W.  Also, I used the USB-C adapter from the docking station in addition to the AC power adapter that came with the laptop directly connected to the AC port on the laptop thinking that either one should power the laptop however when both are connected it does not the charge the laptop.  if I disconnect the USB-C plug from the docking station then the laptop AC charger will charge the laptop.

thanks and I did update the 2 drivers listed there and did not change it

I saw your original note that the system won't charge from its dedicated AC adapter while also docked, and although that surprised me initially, thinking about it more, it makes sense.  USB-C can supply a variety of voltages and amperages, not all of which align with the AC adapter, and I suspect the system therefore has to choose a single power source to use.  I guess it could have made sense to give priority to the actual AC adapter connector, but maybe that wasn't feasible for some reason.  I don't know enough about that aspect of these systems.

Anyhow, if the dock firmware is up to date, then there's no need to worry about drivers since USB Power Delivery obviously works even while the system is completely off.  In that case, the possible culprits are the dock's AC adapter, the dock itself, or your system's ability to accept power over USB-C. If you don't have a spare 180W+ AC adapter and/or dock to test with your system (or another system to test with your dock and AC adapter), then I'd start by exchanging the dock and its included AC adapter, since that would be much simpler than exchanging/repairing your system.