Who sold you a passkey? Dealership must request this from Raymond and pay them, then bill you. You should not require a passkey for back up alarm.
If you have Superword, you may access this the back up alarm on the truck's display, in "config" and change the back up alarm to "forks first" or cab first, or on both directions. Factory password is "1" Superword is space, "2" If this does not work, you need Flashware or "DTIC" and it's only available through through an authorized Raymond dealer. Once connected by laptop, flashware will ask for the pass key to make any changes to the truck, like aux functions with foot off deadman...but not alarm. It will set features and superword to default "1" and space "2" Is this truck new, or recently sold to you? If so, dealer should provide this service at no charge
I'm not sure what you bought, superword or Pass key