Like all 3rd party plug-ins that have not yet been validated, Play must first be opened in Logic’s 32 bit mode to validate the AU plug-in. Please see the following steps to do so:
Once this is done, re-open Logic in 32-bit mode and (if necessary) go to Logic’s Preferences / Audio Unit Manager window and click on the ‘reset & rescan’ button. Next, follow the instruction above to switch back to the 64-bit mode. Play should now be validated for use in 64-bit mode.