" I know for a fact that I'm using the correct firmware update file "
Please note the important things is are you loading the correct SIM provider with respect to your emulex card . I was successful after i loaded the correct SIM provider with the correct firm ware . SIM provider need to install on Esxi server through ESXCLI commands
If you are using the LPE series HBA card ,i was not able to find out way to update it through CD .The CD option is available with the OCe series through "One Connect flash" live CD.
If you can send me the exact model i may be able to find the right combination for you.