I don’t think I’m eating enough - but I feel like I am.

How are you tracking your food? Are you weighing everything, or just estimating portion sizes? Have you gone super extreme and cut out anything you don't deem 'healthy'? Eating large volumes of low cal veggies, etc? If you make your diary public, more experienced members can take a look and see where you may be going wrong. Nine times out of 10, it's logging errors and people are actually eating more than they think.

I'm assuming your using the app because you're currently overweight and you want to lose weight?

If so, then you didn't get overweight eating 750cal a day or struggling to eat 1200 cals.

Depending on how overweight you have become and how long it took you to get that overweight you've been consistently eating hundreds if not thousands of calories above your maintenance every day.

Why do you think it is that you've been able to consume two or three thousand (or perhaps more) calories a day no problem, yet all of a sudden you're full and struggling to eat a quarter or less food?

There's not a lot to go on in your post but if I had to guess the problem could be one or both of the following:
1. Inaccurate logging. You're either consciously or accidentally under-reporting what you eat. There's 1200 calories worth of food in your log but there's 2 or 3 times that many calories worth of food in your belly
2. You're forcing yourself to eat foods you don't like (because you've decided they're 'good') and depriving yourself of food you love (because you've labelled them 'bad'). Under eating is easy when you have no appetite for the food you're eating.

Before we go much further, it may be helpful to open your diary.

Also some stats: M/F - ht - wt - age