PlusOne mobile otg data transfer issues

[RavingLoony]

Hi
I have a Dell Latitude E6230 running Mint 17.3. I just got a OnePlus 3T mobile running Android. Ordered & received an OTG cable from OnePlus. This comprises the universal 3C plug to connect to the phone and an A female socket to connect with an additional cable to another device in this case my Dell. I also bought a cheapish A male to A male cable so to plug one end into the OTG cable socket & the other into the Dell. Worked first time & transferred one album as a test. Leave things for a day or two thinking I'd copy the rest of my collection to the one. Snag, nothing works.

The phone is not showing up as a device any more. The only thing that is working in this arrangement is (slowly) charging up the phone.

I have tried the same arrangement on a Windows 10 machine. same result except I get an audible alert but haven't found out yet what that means.

I prefer to use the Linux box as it's quicker than Windoze. Don't think it's the cable. If anyone has any ideas...

TIA