Thanks for posting.
Apologies that your system is not working as expected.
First thing to do is to check that the drivers were installed in the proper order. If not, then it could cause problems. Here is some information from the Dell Knowledge Base that may be helpful.
Flash drives can be set to be bootable in Legacy BIOS and/or UEFI mode, and system BIOS configs can have them set to boot Legacy only, UEFI only, or both (if UEFI is enabled along with Legacy Option ROMs). Make sure that the flash drives you're trying supporting being booted in the mode that your system is configured to allow.