Pls provide the error message.
Do you run the BIOS Upgrade "As Administrator"?

This is the latest BIOS: 1.10.1

https://dl.dell.com/FOLDER06895661M/1/Latitude_5X00_Precision_3540_1.10.1.exe

Thx!

Peter

Welcome to the Dell Community @jvw 

First method:

Create a new folder on your desktop named “BIOS Update”

Then download your BIOS update.

Dell Latitude 5400/5500 and Precision 3540 System BIOS:

https://www.dell.com/support/home/en-us/drivers/driversdetails?driverid=8ppv7&oscode=wt64a&productcode=latitude-14-5400-laptop

Copy the update to that folder you just created.

Close all Windows and Apps you may have open.

Go to the folder and right click on the update file and “Run as Administrator”

Second method:

Create a bootable USB drive using “Rufus”

https://rufus.ie/

Copy the BIOS update to the bootable USB drive you just created..

Insert USB drive, power-on and start tapping the “ F12 “ key.

Boot from USB and run the BIOS update.

After reboot test and post any results.

Best regards,

U2