I think that you have answered your own question. You can't expect to arm partition 1 when trying to control partition 2. If your actual system only has 1 partition then you need to ask your dealer why he has set up more than one partition on C4 (or why he as set up partition 2 rather than 1 which really won't work). You could try clicking (not sure that one clicks with ones finger... But clicking sounds more correct than touching) where it shows Partition 2. This should give you the option to change to partition 1. You can then try arming from there. That said, reading your description, I am a bit doubtful as to whether partition 1 will have been set up correctly? My best advice is to call your dealer!