Figured I would further confirm this... I made a warlock and took devil's sight. It did not apply the buff correctly and I get blinded by darkness. I also think it's strange that the invocations you select aren't listed on your character sheet.
I have tested this on multiple characters. Devil Sight does indeed not get attributed to the character when taken at level 2. At first i thought it might be a Tiefling(character with Darkvision) problem and the game being unable to overwrite the Darkvision attribute. I have also tried to replicate this with both Drow and Halfling. I used Drow due to their Superior Darkvision and with a Halfling due to having normal vision. Both characters had 0 change happen to them after taking Devil's sight.All 3 characters were unable to see inside of Darkness even though they should. And the Halfling couldn't see normally in non magical darkness either, my Halfling still had normal vision while going around in the Chapel which as very low to no light.