Hi all, I am trying to get one of my players to add feats to their sheet, and all they get are 2 homebrew feats and the critical role firearm specialist one. 
I own all the basic books(phb, dmg) plus multiple source books (tce, xgte, egtw, scag etc), so there should be heaps, as my other 4 players don't have this issue when they try to add feats. 

All the content is shared on the campaign correctly from my side and when i try to add a feat to their sheet it shows everything correctly. 

I am unsure where I should be getting them to look on their sheet, as it doesn't make a lot of sense that it's working for 4 others and not this Dndb account. they also had this problem attempting to pick their race when going through character creation, so it's possible it's on their account somehow, but I'm unsure where to look or advise for that as its all working from my side. 

this is from their phone. 

Have your player check that their Account Entitlements are in sync: (https://www.dndbeyond.com/account/marketplace).

Thanks for the reply; they don't own anything on DNDB, I do, and I'm the one sharing it with a master sub. Which specific section should they as a player be checking in there to allow my content to flow into their account? 

The very first section labeled “Account Entitlements.” Those also include entitlements from shared content. So again, have your player check that their Account Entitlements are in sync.

Awesome, thanks for that, that seems to have worked for them, I appreciate your assistance with this!