Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select Saute function. Melt butter and add pancetta; cook until crispy, about 3 minutes. Add Brussels sprouts; cook until golden, about 7 minutes. Pour vegetable broth over Brussels sprouts and sprinkle with salt and pepper. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 3 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove lid.