I use the Android Stack Exchange app for most of my SE activity nowadays. Just now I've noticed that I can no longer upvote comments: after tap-selecting one, I get a profile icon button, a "COPY TEXT" button, and a three-dots menu that only contains "Share".
I'm not sure when exactly I last upvoted a comment, but it was likely within the last week, and possibly the last few hours.
I'm using version 1.0.89, which hasn't been updated since September of last year. Was there a server-side update that changed this? Or perhaps something has changed locally on my device (I'm definitely still logged in)?