I suggest you follow the instructions here for updating OSPi: http://rayshobby.net/mediawiki/index.php?title=Python_Interval_Program_for_OSPi#Updating_the_program.
Git pull won’t work if you are updating from 1.8.3.
You can also just delete the folder and clone a new one (after saving settings or writing them down). The clone command is:
git clone https://github.com/Dan-in-CA/OSPi