Good day, thanks for your question. You can try to send a feedback via the app if you will be able to do it from there, you can also send a feedback via the Feedback Hub app by pressing Windows key + F from a computer so that the relevant team can receive it, and hopefully it will be resolved on the next update. At the time being, you can try to access MS Rewards from a browser via https://rewards.bing.com/.
Regards,
Paul R.