So I am having this problem where I cannot get the option to add my homebrew subclass to a base class in character builder. I have activated Homebrew content and have even checked to see if the subclass has the correct base class, which it does. I have tried to create this multiple times and it doesn't work. Could I please ask for assistance with this?

Can you publish the subclass and link it here? I'll test it out on my end.

have you checked if the subclass is part of your sudclass collection? 

DO NOT PUBLISH YOUR SUBCLASS!!! If you do you can no longer fix it.

What class is your subclass for, and what level is your character?

Also, please see the General Homebrew FAQ #5: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq).

Once published, could they not just make another copy of it that is editable? I did that with a published monster I made to make a newer version.

Yes, but that’s sloppy and the old version will always be out there for people to download, you can’t ever get rid of it.

Oh shoot, I didn't know you can't delete your published homebrew. That's a bummer.