Double-clicking a file doesn’t open the associat ed app

Check that files of that type are still associated with the expected app: select one, press ç+I and ensure the app is listed in the “Open with” section. If the wrong app is listed there, pick the correct one from the pop-up menu, then click the Change All button to set that as the new default app for this file type.

If the app is already running, it may have hung. Press ç+ Alt+ oe to bring up the Force Quit Applications dialog and check whether it says “Not Responding” alongside the app’s name. If it does, select the app and click the Force Quit button, and then try doubleclicking the file again. If not, try dragging the file onto the app’s Dock icon, or using the app’s File > Open command.