Prostar Interaxle lock

[smorgan87]

Got a 11 prostar and the diff lock doesnt engage. I flip the switch and it start beeping at me until i turn it back off. Had a buddy looking at it with me and we found the hose into the front diff airs up and i can hear air flow when i toggle the switch back and forth. Any suggestions? Aside from burning the truck. Ive joked about that already so insurance might find it sketchy.