Project Duration stuck at 600

You can't change a project's duration from the Settings (formerly Preferences). Note, that the setting you have in your picture is the default project length when a new project is created, it will not change the time of an existing project.

There are two ways to change the duration of an existing project.

1. Go to the project properties (command-J) and change the duration parameter.
2. In the playback controls to the right of the timecode, there is a stopwatch icon and a downward pointing arrow. If you click on the downward arrow, it will give you a menu, select "Show Duration". If you click the stop watch it will toggle two blue hands and two white hands at 1/4. make sure it is the two white hands, this is the show duration setting. Now you can type in a new duration.

Once you change the duration you may have to zoom the timeline and adjust the play range.

Hi

GFXZen is correct. I didn't notice in your screen shot that you are trying this from the preferences. You would do this from the properties within the project or the alternative method Gen describes. Once done, use the reset play range option.

Hi

Go to your menu - mark - and select 'reset play range' Note keyboard command.

Your play range is set to 600 frames.

Zoom out the timeline a bit. Drag that white triangle marking the end of the play range to extend it.