Wont Create Library - Not USB Error

I've had a strange issue arise out of nowhere. 

Using Rekordbox on my Mac about a week ago, I put some new playlists on there for a gig as normal (exported then eject through rekordbox to create library)

I didn't notice at the time but it did not create the library, I noticed when at the gig and my new playlists weren't there ...

I came home checked the USB's; the playlists were on there, I tried creating a library again and the drive just drops out.  I tried two USB's and that same. These are good quality USB's that have always behaved in Rekordbox, and have already plenty of tunes on there from Rekordbox.

To rule out my USB's I formatted them both (Correctly to the proper format) and still not creating a library. I tried updating Rekordbox, and even reinstalled it with no fix.

Here is the even more strange part.. I keep my master database on my external hard drive, so I booted up Rekordbox on my old Mac with the same database on my external hard drive, you would think the problem would still be there but it's not. It works perfectly wtf. 

So my current sitch is using my old 2010 Macbook for Rekordbox instead of my 2018 Macbook (which has worked perfectly for the last 6 months I've had it till now)

I can't see any posts addressing this directly so I'm asking for help. 

Using a 2018 15' Macbook Pro on macOS Mojave 10.14.6