In Safari version 11, Apple now automatically blocks any auto-playing audio, or video that contains audio. In Planning Center Services, we don't really auto-play audio, we wait for you to take an action. However, when you click a file or the media player button, your click technically opens the media player, and then we auto-play the file you just clicked. So if you use Safari 11, you'll now need to click first to open the media player, and then click the Play button to start playback.
Safari does, however, give you the option to turn on auto-play for individual sites. By allowing auto-play for Planning Center, you can avoid that extra click and play files as quickly as before.
From the Safari menu, go to Settings for This Website... and then change Auto-Play to Allow All Auto-Play.
The first time you access the Media Player from Safari 11 with auto-play not allowed, Services will pop up an alert informing you why your file didn't play with a link showing how to enable auto-play.