I realise this is an old thread but hoping someone may reply - my L&D team are using Rise and the imsmanifest still does not include any masteryscore code, so I have added this in using the steps shared by Nathan above. However, there was already this line in the imsmanifest:
<adlcp:dataFromLMS>eyJjcHYiOiJiWHJzT1RhVCIsInJsZCI6ZmFsc2V9</adlcp:dataFromLMS>
I deleted this line and replaced it with: <adlcp:masteryscore>80</adlcp:masteryscore>
Then rezipped using the correct level of folders.
The good news is that this now shows a mastery score once loaded into our LMS, the bad news is that the module will now not load once opened:
