It may take a few months to get used to eating more…both in volume and in calories. You are not even 6 months post, so you may be limited in your volume ability.
You dont need to eat 1200 cals today…just aim to get there eventually (and trust me, you will).
I reached goal at 7 months, and it took me 4 months and an additional 15-ish lbs lost before i found my maintenance balance. For me, this was about 2000 cals a day at that time. Which honestly was a Herculean effort as I too was sub-800 cals throughout weight loss phase.
I got full really quickly back then (and still do today, but to a lesser degree) so i relied on chicharron (i.e., pork rinds/cracklins). I know, I know, its really high in fat so it may not be everyone’s bag, but for ME it was high in protein, zero carb, and did not stuff me like meats did/do…and its SUPER high in calories.
Im 3.5 years out now and pretty much have been maintaining my weight ever since (+/- 5 lbs), and average about 1800 cals these days (eating all sorts of food, both healthy and not-so-healthy, and yes, i even eat bread now, lol)
Do what you can, a little bit at a time, and you and your body will get used to more calories AND volume eventually.
Good Luck! ❤️