Whenever I try to go and select an artificer specialist (level 3), There are no options to select. Am I missing something?

On the “home” tab of the character builder, the toggle next to “Eberron content” needs to be on (red, to the right). If you have access to any of the subclasses, they should be available when you do that.

Eberron Content is enabled on that character. Do I need to buy the artificer/subclasses? I did some digging and it seems like you need to buy the artificer class?I was able to select it normally when I made my most recent character but when I try to make a new one I cant. Sorry for any confusion, pretty new to DND. 

If you purchase any of the subclasses, you get the class. Yes, that is how you unlock the subclasses. You must have had the content shared with you at some point which permitted you to access the class. You can purchase any one or all four Artificer Subclasses from Tasha’s Cauldron of Everything.

Does content sharing not access the subclasses for artificer? someone in my campaign is apparently content sharing like you said.

Only if you are in a campaign with sharing enabled and someone in that campaign has purchased the subclasses and that character is in that campaign.

He said he has the artificer subclasses purchased, I just cant select any for some reason. I can make manual subclasses though

 The person with the content/content sharing is in the campaign and owns the the artificer and its subclasses to be clear. 

Is your character in the same campaign? Has content sharing actually been enabled for that campaign?

edited the last comment a bit late, but yes the character in question is in the campaign with the person that has content sharing enabled. 

I think one of us is misunderstanding.

The person doesn’t get content sharing enabled. The person has to enable content sharing for that campaign. Has sharing been enabled for that specific campaign?

Yes, it is shared for the campaign

Have them click here and make sure their entitlements are synced:

https://www.dndbeyond.com/account/marketplace

Then have them turn content sharing off and back on for that campaign.

his entitlements are in sync, Ill see if he can turn the content sharing off/on again.

Hello. Did this work? I am the DM of campaign and went through all the troubleshooting above. I know how to check sync and disable/enable content sharing. I have the Ebberon source books shared as well as PHB amongst other things. His character has Ebberon enabled. Still the same result. He has no options for his specialist class.

Here is the public link to the character.

https://www.dndbeyond.com/characters/16591651

Edit: also Tasha's is enabled content sharing for him as well.

The character sheet you link is using the UA version of artificer. Is this because they can't see the actual artificer class?

I'm not sure how i ended up with the UA version, but I was able to delete the class and assign it the right version of Artificer! Thank you for pointing that out. 

I encountered this same issue — playing an Artificer, in a campaign where PHB and TCOE sourcebooks were shared; when levelling up, my Specialist and Feat options were empty.

To resolve: I visited the Campaign screen, then selected to "View" my character (not Edit!!); when viewing character sheet, selected "Manage Character", and then all of the expected editing options were available.