Combine cranberries, sugar, port, and salt in a multi-functional pressure cooker (such as Instant Pot®). Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build.

Release pressure using the natural-release method according to manufacturer's instructions, 10 to 40 minutes. Unlock and remove lid. Add cinnamon stick and select Saute function; cook until sauce thickens, 5 to 10 minutes. Remove and discard cinnamon stick.

Blend sauce with an immersion blender for a smoother consistency. Let cool; sauce will continue to thicken naturally.