Start of year Marriott IT glitches.
Give them a while to sort it out and correct the various numbers you are seeing on your account. You will still need to accrue 50 nights to Platinum and the app will keep your running total for you as normal throughout the year. You can evidently already see your 15 qualifying nights from your credit card. Their IT is just going through a rough patch caused by the startling event of the year going from 2019 to 2020 and various account fields needing to be reset or updated for all the members.