These pictures say everything. Somebody stole the review button in the small design (mobile).
And to prove that I see the buttons on large screens:
Also, this was a recent change (last few days) because previously the review icon was shown in favor of the help menu. Removing the help icon happens for high-reputation (10k?) users on large screens too, so this is probably a bug.
How shall I continue reviewing on my mobile phone, when I can't see the button??