When looking at stats in Day/Month/Week/Year, tapping each bar should change the stats shown to reflect the day I'm trying to look at.
In some cases, tapping the bar changes which bar is highlighted, but doesn't change the stats shown.
For example, this screenshot shows 1 view and 1 visitor, but the bar selected shows close to 30 visitors.

This has been tricky to reproduce, but I've had most luck with opening a site I've looked at stats for recently. Sometimes, the app loads the stats (it will give a loading screen between tapping on bars) and everything is fine. Sometimes, it doesn't try to load anything.
Tapping the < and > arrows seems to work even when tapping the bars doesn't.
Here's a video:

Four user reports so far, #2127720-zen, #2145011-zen, #2142342-zen, #2145194-zen
More detail on all those reports: https://wp.me/p7cLQ7-Da
@danielebogo another one for you, thanks for the report @thehenrybyrd .
Had another report in #2149095-zen.
It sounds like you're already working on this, so let me know if I should stop reporting and start telling folks to look out for a fix. 馃槃
And another in #2148632-zen
New stats aren鈥檛 working in my app. If I tap another day鈥檚 bar graph, it continues to display today鈥檚 number.
One of the original reporters came back with another gif for us in #2142342-zen.
In this case, it seems whenever they open the app and go to stats, they see the stats sticking until they use one of the arrows to move to a different day. https://wp.me/p7cLQ7-Da /#comment-1211
Thanks @thehenrybyrd ! I'm working on it here.
@danielebogo I'm still seeing this issue in the 12.8 beta - can you let me know when this will be live for us to try out?
@thehenrybyrd this has been fixed in the 12.7.1 release but not merged in 12.8 beta yet.
@jkmassel is working on 12.7.1 hotfix submission.
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@danielebogo another one for you, thanks for the report @thehenrybyrd .