Players can't access player handbook

I purchased player handbook and dungeon master guide and a master tier subscription. I created a campaign and enabled content sharing and my players can access everything except the player handbook.

Be sure you have content sharing enabled in the campaign they're in. 

Also, they can try to clear their cache if they attempted to view the item previous to your purchase:

It is likely that your browser has the link to your content cached, which can be fixed fairly easily, by clearing your browser's cache.

If this is not something that you are familiar with, you can find useful guides here on how to do this for most current browsers.