We have the same Ventura IV. I do not have to do anything with the ignition, as the Aladdin isn’t powered through it. Just move one of the joysticks forward or “up” to turn the Sony and Aladdin on. All the Aladdin features come up except the ignition does have to be “on” for any engine-related data to display, which makes sense. It’s been awhile since I’ve used the TV aspect, but I think the TV(s) has to be set on specific “Input 1” to display the same Aladdin screens as the Sony. But that’s aside from your issue.
My guess is that the Aladdin feed is disconnected from the back of the Sony, or from the “VCM”, Aladdin Video Control Module. I say that because techs or owners more frequently fool around under that part of the dash, and stuff happens. There should be a black wire and plug in the middle lower back of the Sony, visible with a flashlight if your top dash access port is open. That is likely the main Aladdin feed. On mine there are also 3 small wires, green, black, and fused white that are plugged in streetside of the big black one; I’m guessing they are for the side cameras I had BCS install at delivery, and perhaps the rear camera. I can’t see enough of the Sony’s back to read port or ID info.
As to the VCM, I haven’t seen mine but if I were to be ambitious about it I’d open the upholstered access in the side of the driver’s left switch panel, next to his left knee, and check in there. It should look like the image below. If you can find the VCM, the TV lines should run from Output #1, yellow video top, white audio (L) middle, red audio (R) bottom. The screen video feed I’d guess should be one of the remaining two top outputs. Assuming that is properly connected, I’d then suspect the engine and house bus connections on the left of the VCM, but not if you have those come up on the TV okay.
All that said, there is on mine in the 12v electric bay, streetside foremost, a “J1939 Bridge” that’s not on any of my Aladdin diagrams or descriptions, and that has 12 connections that may be involved with or causative to your situation. You might check it for high resistance connection issues if nothing else mentioned is obvious.
Sorry not to be able to guide you directly to the VCM. For more info, check the Coach Assist section for a copy of my electrical diagrams book, which you should have anyway given its the same coach. There are also more than one manual and troubleshooting documents for Aladdin in Coach Assist; you might peruse those. I believe there is an ‘06 Monterey owners manual there, pg. 165, also, if you need basic Aladdin guidance for adjustments or Sony screen use.
Joel