Daily Challenge Daily Streak Calculation Bug
I started yesterday's daily challenge at 23:55 GMT and finished sometime into today. This reset my "days played in a row" to 1, which increased to 2 upon completing today's challenge - but as you can see, I've completed the challenge for (at least) all of the last 7 days.
It's probably just calculating days played in a row as the completion time as opposed to just number of consecutive daily challenges completed.
Fairly niche issue.