I'm not a CTIS expert, but I do have a working system. Look at the flashing lights carefully, is it 4 or all 5? 4 is a low tire and 5 is a failed control module. CTIS doesn't work well at less than 120psi. Once you reach 120psi, press both lower red buttons simultaneously, it should start to inflate the flat tire. Your leak is likely the tire or rim seal, as the CTIS only inflates or deflates the tire, then the valve on the rim, if working correctly, isolates the tire pressure from the CTIS system. Normally, it checks tire pressure every 15 minutes. In run-flat, it checks every 15 seconds. Emergency button is a super-low psi setting if truck is totally stuck.
Again, search CTIS posts here and read the manual areas specific to what you need to know first. People want you to at least spend 15 minutes searching for your own answer, and at least within the posts, and respective area(s) of the manual. Do you have to read the entire manual? Not at first, but you'll for sure know more about the truck once you do. Tire and wheel weigh about 350-375lbs each.