I am not seeing crossbow expert in the list of feats even though I have purchased the content.

Check your entitlements on this page. if it says you need to sync, click the sync button. While you are on that page, scroll down to “current product licenses” and make sure The Players Handbook (or the feat, or the PHB feat bundle) shows up there. 

 As far as I can see everything on that page is correct I cannot see anything to do with sync.

Allow me to consolidate all the most frequent advice when this comes up, please bear with me if you've tried some of this already.

• Does someone in the campaign have a subscription that allows for them to share content and do they have content sharing enabled? If neither of these things is the case then you would be unable to have access to the content.
• Are the players making the character in the campaign that the content is shared with them? They will only have access to the content in the character builder if they are making the character within the campaign.
• Toggle the content sharing on and off again. Simple as that.
• Do they have the necessary sliders toggled to allow them to use said content? Make sure that the slider is red (to the right) to have the content enabled. Linked here is an article written by the staff of Dndbeyond about how the sliders work and what each slider actually enables.
• Have you made sure that you and your players have their entitlement in sync? You can go here to ensure that all content you should have access to is being properly mapped to your account. If you don't want to follow the link you can go to the drop-down menu that pops up when you hover on your username at the top right of the page and click Account->Marketplace. You should see something that will tell you to sync your entitlements or that your entitlements are in sync.
• Do the players have access to read the content on Dndbeyond but not access to it on the character builder? If so, you may have purchased the compendium only part of the book which allows you to read the content but not use any of the tools in the character builder. The best way to check this is to go to the market page for the book and see if you have the checkmark next to any of the stuff aside from what is labeled 'Compendium Only' at the bottom of the page. If you only own the compendium content you'll need to buy the integrated tools to be able to use that content on the character sheet.
• Try using a different device or just wait to see if it fixes itself. Sometimes the servers on Dndbeyond are slow. It can take a while for the stuff to update for your players. Maybe there is some backend work that is happening that is temporarily stopping you from accessing that content. These things happen. I've been in situations where my players have problems with content when they make a new character and about an hour later those issues are gone. I can't explain it, sometimes you just need to wait.

If any of these you have tried and didn't work, please let us know as much information as possible in regards to each one so we can try and figure out where the problem is. 

Where is crossbow master i don't know