Set the Instant Pot to sauté and add the olive oil. Cook the onion, carrots, and celery for 3 minutes until they begin to soften.
Stir in the garlic and cook for 30 seconds more.
Add the split peas, potatoes, vegetable broth, thyme, bay leaf, salt, and pepper. Stir once to combine.
Cancel sauté mode, secure the lid, and set the valve to sealing. Cook on manual high pressure for 15 minutes.
Allow a natural pressure release for 10 minutes, then quick release any remaining pressure.
Remove the bay leaf and stir the soup. Top each serving with fresh parsley.