Starting on Wendnesday last week 2/15, all visuals in our dashboard that relied on internal functions (like TODAY or NOW) stopped working. Our dashboad is published to a workspace and uses a "Mixed Storage Mode".
As a temporary workaround, we made an alteration to our workbook (we removed a table) so that it could become "Direct Query Storage Mode". Publishing as Direct led to our visuals working again.
We can recreate the issue by adding table and publishing it as "Mixed". Calculations will again fail, if they rely on internal functions like TODAY.