Often sign-up campaigns offer different points depending on what sign-up channel they used. Please see If the guest was not awarded the correct points, it is possible that the logged on via a different channel than they expected or reported. For an explanation of channels, please see What are the different sign up channels?
Here's an example:
Guest A has reported that he signed up via Facebook and should have been awarded 75 points, but only got 50 points (non-Facebook)
Reviewing the guest time-line, you can see that the guest actually initiated the sign-up via his mobile app and then connected it to the face book account. This is not the same as signing up via the Facebook channel and the guest is not entitled to the 75 point award.
Guest B did sign up via the Facebook channel and was awarded the 75 points. (Facebook).