MacOS Sequoia and Opt-based hotkeys
Starting with macOS Sequoia, Apple does not allow global hotkeys where Option or Shift+Option are the only modifiers. This is an intentional decision on Apple's part and it's not going to be fixed. More Details.
Every other sandboxed app is affected, and apps that are not sandboxed seem to keep working as before. Shottr is sandboxed and is affected. Removing sandboxing would allow the app to process every keystroke and look for any key combination, but doing so would make the app less secure, and I decided against it for now.
Solutions
1. The easiest way is to add Command or Control to your key combination. Something as simple as replacing Opt with Ctrl would solve the problem.
2. If you're using Raycast, you could install Shottr extension and assign any hotkey to any Shottr action through Raycast.
3. You could also use an app like BetterTouchTool or Karabiner Elements to remap your desired hotkey to an alternative hotkey accepted by macOS for Shottr.