When staff reward on SIMs they need to make sure they are not using more points than they have been budgeted to use on Vivo. When staff exceed their budget, not all the points will process and SIMs and Vivo will reflect differently for students.
If you find this is happening please go to setup>manage data>add/edit staff roles and increase the weekly budgets for your staff. (You can always keep an eye on staff in the statistics area and see who is over rewarding.)
Please make sure to check the budget section and that there are enough Vivos in the budget as well.
If the problem still persists please contact firstname.lastname@example.org