Access to music on the USB flash drive of the other player

Legacy Products Engine PRIME
1

I have the same set-up with the same connections as always. i use

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Engine Prime 1.6.1 & SC5000m Engine OS 1.6.1. yesterday I exported via EP several usb flash drives that work well on the player where they are connected, but on the other player when I select this warning appears. does anyone know the reason for this? in 3 years of SC5000 I’ve never seen