Set your Instant Pot to Sauté mode. Wait until it says HO, and add the olive oil.
Season all sides of your short ribs generously with salt and pepper.
Add the short ribs to the insert, and brown each side for 4 minutes. Do in batches if necessary to not overcrowd the pot.
Remove ribs from Instant Pot once browned, and set aside.
Add the sliced onions, to your Instant Pot, and sauté until soften. Then add chopped garlic.
Add chopped carrots, celery, fresh thyme, fresh rosemary, and bay leaf and sauté for a minute or two.
Combine the Coca-Cola, beef stock, and tomato paste in a separate bowl and pour into Instant Pot with veggies and spices to deglaze the insert.
Scrape the browned bits off the bottom of the pot with a wooden spoon, and give it a quick mix.
Add browned short ribs to the pot and cook on High for 15 minutes.
Once done cooking, let the pressure naturally release for another 10 minutes or so.
"HOW TO MAKE INSTANT POT SHORT RIBS"
https://bellalimento.com/2019/11/09/coca-cola-braised-short-ribs/#:~:text=HOW%20TO%20MAKE%20INSTANT%20POT%20SHORT%20RIBS