You have the A442F gearbox
The little wire that looks like a bicycle brake cable which goes into the red is what Chris et al is talking about.
Grasp it where it is arrowed and pull it gently away from where it disappears down the tube with the red end. It should move freely but spring back under a little tension. It shouldn’t be sluggish or feel like it doesn’t want to move in either direction. It looks ok from the photo but you need to give it a pull.
The black pancake with electrical wires coming out of it is your throttle position sensor. Unless it’s been moved or has something broken within or about it then it probably isn’t your problem. Problems with the electrical side of these tend to cause the overdrive light on the dash to flash. If this happens there is a very simple process to find out what the system thinks is wrong.
Sorry to ask this again but when you checked the oil did you follow the procedure?
Best to do it with the box fluid hot. Cycle through all gears with the engine running then dip the box. Once it’s hot read off on the ‘hot’ mark (Best) or if cold read off on the cold mark. The thing is, it could be getting warm so could skew a cold reading hence best to do it when the gearbox is hot.
Another test to do is does your gearbox stay in the gear selected, ie in 1, first gear, 2, first and then second, and does the overdrive turn off and back in again? Does reverse work correctly.
If you can post the answers to all the above with accuracy it will go a long way to help others on here help you.
Keep going Kiera, you’re doing great.