This is due to a bug in recent versions of the Google Chrome browser.
We are very sorry for the issue. It's not a bug in CrankWheel but rather in Google Chrome, but we are working to resolve it both with the Chrome team and also by ourselves trying to figure out and submit a fix for the Chrome browser. We are committed to getting you back full functionality of CrankWheel as soon as we possibly can.
To get normal functionality back, for most users it is sufficient to follow the steps in this workaround video: https://www.loom.com/share/eaf5270b3b1c43ac92eed2f461dffb52
We've had reports from a handful of users for whom the steps above do not work, nor does fully exiting the Chrome browser or even rebooting their computer. If this happens to you, please do as in the video to disable the extension (toggle it to the left) or uninstall the extension, and leave it disabled or uninstalled. You can then screen share starting from https://meeting.is/ss
The page there will show a "Start screen sharing" button that should work for you. It will also show an "Open CrankWheel" link that you can drag to your browser's bookmark bar (on Chrome, hit Ctrl+Shift+B to toggle its visibility) and once it's been dragged to the bar, you can click it to launch CrankWheel at any time.
We will update the messaging on the https://meeting.is/ss page once the issue has been resolved.