Using MacOS Catalina 10.15.7
Adobe Creative Cloud Illustrator 2021 25.0
Using polygon or star tool, pressing up/down arrows (while mouse down) does not change number of polygon sides or star points.
I checked preferences and it's not the keyboard increment setting (since up/down works with the selection tool).
Similarly, up/down keys for increment/decrement functionality doesn't work for line tools either (arc, spiral, rectangular, none of them)
How do you use it?
You need to press the keys while the mouse button is still down when drawing the shapes.
Yes my mouse button was down and I did not release it; I have been doing that. Dragging out the shape while pressing the up/down keys (while mouse down means I have not let go of the mouse click; indicated by the outline still being green and the size still changes changes as I move the mouse).
What else is running on your system?
Some applications and extensions "steal" the keypresses. The Chrome browser is an example, but also screensharing apps and antivirus. Can you shut down everything and launch only Illustrator and try again?
The up/down arrows still work when I use the selection tool. If other apps were overriding the arrows, then I wouldn't have been able to use the selection tool to move objects up/down. So far I'm finding it's the mouse-down combo that's an issue.
I restarted my machine to make sure no other apps were running; no difference.
I checked my keyboard preferences, went through the shortcuts and deselected ctrl+up and ctrl+down, even if they contained ctrl, just in case; no difference. I couldn't see any other shortcut tied to the arrow keys.
I uninstalled and reinstalled v25, no difference.
I uninstalled 25 and installed a previous version 24.3, no difference.
For the record I'm using:
Do you use an antivirus?
Which one is it?
The most recent Illustrator version update might've helped because it's working now (it was updated from v25 to v25.0.1 November 28th)