I was trying to prepare a Human Variant Cleric with the Warcaster Feat, but when I select Feat under the Race feature, it just says select Feat, no options are listed.

that should be a drop down you can click on.

Can you link to the character (from the URL bar, not the share link) with everything but the feat selected?

Have you purchased the warcaster feat?

I can not remember whether there or no free feats or one but the vast majority of feats you have to purchase .  

The other thing I can think of is you must have the ability to cast at least one spell, that might mean you can't take the feat if you have no spells prepared.

Quote from Jegpeg >>

The other thing I can think of is you must have the ability to cast at least one spell, that might mean you can't take the feat if you have no spells prepared.

While that is technically a requirement for War Caster - it's not currently enforced. I'm able to add that feat to a level 1 Fighter with no access to any spell.

I was on a sponsored campaign, so it should have been unlocked.

Thanks guys, I check the campaign and content sharing was removed, I'm surprised that was locked though...