I have copied this from the official kodi forum. It is referring to the official kodi repo which should be installed by default.
See if it works.
Btw i do not have this addon installed so cannot test for you.
"Which version of Kodi are you running?
For up to date versions, you should find it in the official repo (the built-in one).
First from the main menu go Addons > My Add-ons > Videoplayer InputStream and if it's there select InputStream Adaptive and check it's enabled.
If it's not installed, go to Addons > Install from repository > Kodi Add-on repository (you may not need this step if you have no other repo's installed) > VideoPlayer InputStream and install it from there."