Gave GTAC a call since I was not getting any response here. Per usual, the engineer that answered the call was able to provide a solution. Using our key file in x.509 format, running the following on the Linux appliance resulted in a PKCS#8 key file that, used in conjunction with our crt file was installed successfully.
openssl pkcs8 -topk8 -in -out server-pkcs8.key -nocrypt
