[2022] Core Challenges currently not available?

Dear Ubisoft,

Up till yesterday night, core challenges have been presented when I play AC Valhalla.
But this morning when I logged onto Uplay & started AC Valhalla, then clicked on "Ubisoft Connect", they are no longer available.
Time Limited Challenges: still present, no issues
Core challenges tab now shows "Core Challenges currently not available".

Is this a temporary thing or have core challenges for AC Valhalla been removed permanently as of today?
If it's temporary, when will the core challenges be restored?

Thanks!