"Time spent today" remains at 0 !

On Lingvist each day for two weeks now. But since midnight today, in the "My progress" section, "My time spent" remains at 0, while I keep practicing. This is also the case for "new words"... Is this a known bug ?
I can practice but cannot see my progress anymore.

Up to now wonderful, efficient and addictive app !! Thank you so much :)

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