I have found that I the Instrument of the Bards is not available to add to my inventory. Does anyone know what's going on with that? 

Can you confirm either of the following:

1. You own the Dungeon Master's Guide, or
2. You have individually purchased the Instrument of the Bards, or
3. You are in a campaign where the following are all true:
   1. Content sharing is on
   2. You are editing/making a character within that campaign
   3. Someone in that campaign has access to the Instrument of the Bards

Instrument of the Bards is not a Basic Rules/SRD (aka free) magic item and is only found in the Dungeon Master's Guide

Instrument of the Bard is not free. If you want access to it, you need to own the DMG, own the item itself, or have the character be IN THE campaign with Content Sharing with someone who has it.

I have, that's the thing I have the books but it does not show up for my characters at all. The only books I don't have are a few of the more recent releases or preorders. That is why I'm confused.