First, sterilize the jars in the Instant Pot: Insert the trivet, add 1 cup of water, put the jars in the Instant Pot (IP) (I could only fit in 2 at a time). Close the lid, lock and set the valve to sealing. Select manual for 1 minute. You can keep the jars in the oven to warm or in the IP while you work on step 2. Repeat Step 1 if needed for any extra jars.
Peel mangoes and chop into one inch cubes. Use a hand squeezer to extract a half lemon’s worth of juice. Be careful not to let any seeds fall through. Add lemon juice to your chopped mangoes.
Put the mangoes/lemon mixture in the Instant Pot. Add the granulated sugar. Set to manual pressure for 1 minute. Let it naturally release the pressure. (This took about 5 minutes for me)
Once you can open the Instant Pot after Natural Pressure Release (NPR), the sugar will have dissolved. You can choose to either use an immersion blender to puree the mangoes. I chose a masher to coarsely process the mangoes.
In a bowl, add the 1 3/4 cup of apple juice and use a whisk to dissolve the package of pectin.
Set the IP on saute. Add in the pectin/juice mixture. Keep stirring using a wooden spoon for 8 to 10 minutes, until it starts to thicken. Hit the cancel button. Keep stirring for a minute.
Use a ladle to scoop into four 500 ml mason jars, leaving 1/2 inch space to seal. Apply lid. Cool in refrigerator until set.