I just upgraded from 16 to 17. Scroll bars in all apps work as expected, but when I click on the scroll bar in the main menu, the menu just closes.
Hmm, I seem to have a self repairing OS. I came back to the laptop, woke it up and the scroll bar was working properly. Let's hope it stays that way :^)
When You have tested it more and it will work, please call back. Then we can close this Thread.
Thats a strange issue you have faced, although looks like it was only temporarily. Hopefully, you don't have anymore issues with the Os. But as Ponce said, please let us know if you have any further problems.
Also, I'd like to nip this in the bud early, since its highly likely, you are using Wayland, since its unfortunately the default display manager in Zorin OS 17. When you get to the login screen, click on your name, then click the cog wheel that shows up, switch to Zorin OS Desktop on Xorg.
Making that change alone, should prevent future issues. And make sure to double check you are still using Xorg in the future as well, after you make the change, just to be insured, you will still be using Xorg.