RAW file Media Offline?

I have a .raw FILE on an EXTERNAL HD and when I import to Davinci it blinks "Offline Media" in red but the clip plays great in Blackmagic Raw player. What gives? When I try to combine it into my timeline as Ultra HD and Deliver, the Deliver process says it could not "Decode" the file and to check it on my HD. Tips?

[Peter Chamberlain]

Usb drive? Speed could be the issue

thanks. thunderbolt 3 connected to external SSD t5. other .braw files work