So I decided to give RB2.1 a try.
To do so, I decided to use my backup computer first, test and if everything works well, migrate my main computer.
So I installed directly the Beta 645 on my computer that never previously had any RB version on it. I entered my license number, and the app opened, with nothing in the screen (except for tags columns) although I have s Serato 2 Pro Library on this computer.
I tried to Drag & Drop my iTunes XML file fist to see if I could see my iTunes Library in RB, without success. When I try to D&D the xml file on the RB window, it would just not take it.
So I exported my Rekordbox Library to XML to try it, and I have the same result with I try to D&D my xml file.
I closed RB. Opened it again, tryed the same things again without success.
I deleted the Music/Rekord Buddy folder. Opened RB, entered the license number. Tried again. Nothing.
Rebooted the computer…. Etc etc. Nothing works.
My computer is a MacBook Air running 10.14.6. Rekordbox version is 5.7. Serato is 2.1.1.
I have to say that my music (and rekordbox library) (and iTunes Library) is on an microSD inserted in the SD slot with a BaseQi adapter. So it is considered like an external drive I suppose.
Oh! Since I tought that the « external drive » could be the problem, I created a new iTunes Library locally on my computer. And when I tried to D&D the xml file from that local iTunes library, I encountered the same problem.