Master slide must use 'Advance on Mouse Click'.

This error appears when advance on mouse click is not enabled on the master slide(s) in a presentation.  This setting will actually override whatever setting is on the slides themselves in some circumstances.  Even if you plan on using timings we still require advance on mouse click to be enabled.  This does not mean you have to use it, only have it enabled. Continue reading to see how to enable this setting.

To add advance on mouse click to a master slide. First, go to the View tab.

Then select Slide Master.

Select the top slide master.

Go to the Transitions tab.

Navigate to the "Advance Slide" section and check "On Mouse Click".

Make sure to do this for all top-level master slides. You can also do a Ctrl + A to select all slides instead of doing them individually.

To return to your main screen, go back to the View tab.

Then select "Normal" and continue editing your Presentation.