I'm having a similar problem. I can't get piercer so show up. I've bought Tasha's and I've had for a while.

Does your character already have that feat?

That was it lol. Thanks 

im haveing the same problem i own all the feats but only 12 are showing up and this isnt the first time this has happened to me

Doesn't really solve the problem but just make sure homebrew content is on then make a custom feat thats just the exact same as what you want. Worked for me with war caster.

Quote from LadyBaguette >>

im haveing the same problem i own all the feats but only 12 are showing up and this isnt the first time this has happened to me

 
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