Lets rewind - i have been looking at the flow of this thread.
You have a respectably sourced
Sandisk ultra USB 3.0 512GB memory stick.
One old B2 with music on
One new B2 that you want to duplicate that music to.
Your
Sandisk ultra USB 3.0 512GB memory stick seem to be invisible to your new B2 and to you Mac PC.
However, you think your "Exported" a backup to it on your OLD B2 OK.
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OK
1) Plug the USB back into the OLD B2 - does the OLB B2 detect its presence? If NOT then you probable did not make the backup you think you did - either the USB stick is faulty, fake or not FAT32 formatted (I Take it you did get your OLD B2
to format the USB stick before you exported to it ?).
2) if the OLD B2 can see it OK, then if you have one to hand and are prepared to erase its contents - please insert a new, different USB stick (of any size leas than 2TB) into your NEW B2 and run the "Format USB A" on it (NOTE this will destroy any data that was on it permanently!!). If this works and the NEW (and OLD if you want to try) B2 can see this USB after a reboot, then the NEW B2's USB port is working OK.
Come back to us after these tests.
Fred