So my DM gave me the Astromancy and the Arcane Grimoire.  We have content sharing on for the campaign and access to pretty much everything.  I cant add them to my inventory on my character sheet or editor page.  I can find both the items and descriptions and I know they are official.  Where am I going wrong?  Why can't I find the items and add them?  

Worked it out.  Only 1 charter can share magic items in a campaign at a time even if they are un assigned. 

That's not true. Any character in a campaign should be able to access anything that is available to them.

If you own the content, check entitlements are in sync here: https://www.dndbeyond.com/account/marketplace

If you don't then the person who has the Master Tier subscription should check they have enabled Content Sharing for that campaign and their subscription hasn't ended. They could disable and re-enable the content sharing to refresh it. They should also check they only have 5 campaigns with content sharing enabled. The campaign must have only 12 players or less.

The items are from Tasha's Cauldron of Everything so you, or somebody in the campaign, will need to have bought those items or that book on here.

Characters need to made in the campaign for access to any sharing. This will not work for unassigned characters unless you're the DM. As a player, if your player character is in the campaign it will have access to anything shared. 

If all the above fails consider posting a character link. You can also consider raising a support ticket using the Contact Us link at the bottom of any page.