I have got device not found error as Switch did not detect the device. I did a reboot to the switch and performed dir usbflash0: then the usb device was recognized and then I was able to upload the new IOS image to switch 3850 using "copy usbflash0:c...

it is not same with c9300 switch sdm does not apply

We need to check the VPN logs to see what error we are getting.