Logitech Options solved the problem for me as well!! I simply deselected smooth scrolling in the Logitech-specific settings and that fixed the issue. Whomever figured this out is truly my hero! Thank you!

What worked for Justin and Sandy also worked for me. Logitech Options was causing the problem.

What Sandy did worked for me as well, Logitech Options was the culprit

I just updated my Illustrator today and got quite a surprise! It is so automatic to use the ALT key. I have a Logitech mouse with Logitech Options. Due to the previous comments, I focused on the scrolling settings in Logitech Options, as mine acting the same as Daniel M. commented. In Logitech Options, I disabled Smooth Scrolling option and now Alt+Scroll works again. Strange.

Same issue, resetting the preferences fixes the issue temporarily but reverts back after a min or 2.

Problem Solved!!

It seems the X-Mouse program is the issue. I closed the X-Mouse program and upgraded Illustrator to 23.0.6 and alt +scroll wheel functioned as expected. Opening X-Mouse, the issue would return. I will leave my comments below for context. Kudos to the previous commenters for actually figuring it out.

Same as what Ashley said below. The alt + scroll wheel function changed when I updated to the latest version of Illustrator (23.0.6). Before the update, pressing and holding the alt key and moving the scroll wheel on the mouse would zoom in and out of the artboard. After the update, pressing and holding the alt key and moving the scroll wheel moves the artboard left and right. Same as holding the ctrl key and moving the scroll wheel. For those of us that committed this operation into muscle memory, it is deeply frustrating for it to have changed. Photoshop and InDesign operate as before, hold down alt and move the scroll wheel to zoom. Furthermore, installing the previous version does not remap the keys to operate as before the update. Please inform all the users, which is probably mostly professionals, how we can make things go back to the way we are used to operating Illustrator.

Update: I downgrading to Illustrator 23.0.2 to get the alt + scroll wheel to zoom as before.

Sounds made up

The new AI update force-reversed my keyboard shortcuts for scrolling left/right and zoom in/out. InDesign and Photoshop are still my original keyboard shortcuts using ctrl+mouse scroll (scroll left/right) and alt+mouse scroll (zoom in/out), but AI won't allow that. AI has forced them to reverse with the update, and when I tried to correct it, it stated that "Menu shortcuts must contain the Ctrl modifier or be a function key", but this isn't true, since when I do alt+mouse scroll, my screen scrolls left and right (so it is modifying on its own), and my ctrl+mouse scroll, it zooms in and out.

I've uninstalled & reinstalled, but nothing has changed the scenario, my AI keyboard shortcuts remain the inverse of all of the rest of my CC suite programs. Seems like a (very, very frustrating) bug.

I had uninstalled and installed the X-mouse button and solved the problem, but the problem returned. In fact, it only corrects if you open the X-mouse button and click on any lucar on it. I don't think I understood Jamet's explanation. Thank you, Jamet.

Yep Samet's comment about xMouse Button Control also fixed it for me. 3 cheers for Samet!

Samet's comment below about the xMouse Button Control worked for me. I was also using this software.
Thanks Samet!

I am using "xMouse Button Control" for organize my mouse button. I clicked this option and this problem solved on my computer.

I've been having this same problem since the 23.0.6 update. Reverting back to 23.0.5 didn't do anything so I reverted to 23.0.3 and it's working normal again. This is a pretty huge issue for designers who appreciate a quick production time. I literally curse out loud every time I go to zoom and it just scrolls sideways a little. Then when I go to zoom out with the shortcut keys, it repositions the art board because I have an item selected (which is a feature I do NOT want to turn off).

I have the same problem. I have tried several options and still have the same problem. Scrolling only works with AltGr (right alt)

I'm unable to downgrade, we're applying for cyber essentials certification which requires having the latest versions of software. If I downgrade I face slowing down the application process which could potentially cause us to lose business.

I downgraded back to 23.0.3 because of how annoying this little change was.

This is definitely a big problem, please fix ASAP. I've reset preferences as recommended and makes no difference.

Same issue with both alt keys, it's ruined my entire workflow, it's like i have to re-learn illustrator again.

As posted on, it DOES NOT affect 23.0.3, just my versino of 23.0.6.

Alt scroll works on Photoshop, but not Illustrator.

Alt+Ctrl+Space still works to enable the zoom tool, but only Ctrl+scroll works to zoom in and out instead of Alt+scroll

Alt+mouse wheel doesn't worked after an update anymore
Alt+mouse wheel doesn't worked after an update anymore. When I use alt+mouse wheel for zoom in or out, this combination works as left-right pan from updated my Illustrator yesterday(19.09.2019). My Illustrator's version 23.0.6 and I am using Windows.