Can't convert from Event to Stream audio

I've put some audio into Animate, and I'm having the typical issue of "The audio will only play on frame 1 and nowhere else". I've looked it up and it says that you're meant to change the audio from Event to Stream from the Properties menu. I go to the properties menu, find the Sync section and click it; my audio is set to Event. "Ok" I think, "Time to change it to Sync instead". I click the menu and all the options are there; Start, Stop and Stream. There's just one problem...I can't click them. Y'know when there's an option in a menu that you can't click because it's a different colour? (Usually grey) Yeah, that's what's happening.

Please help

(The audio is a WAV file by the way)