Total Commander

I'm using Total Commander with the USB-Stick plugin on a Lenovo Tab M8 tablet. This allows me to see files on my USB stick, but I am unable to open them, copy them or move them. The files are Nikon NEF (RAW) images, around 25Mb in size.

I need to get these files open in Snapseed for editing, but so far am having no success. If I click on a file and then select 'Download+Open with', nothing happens at all. The same with 'Download+Edit'. If I select 'Copy/Move/Send via Bluetooth' , I get a Copy/Move screen with a target folder /storage/emulated/0/Download. If I then click on either Copy or Move I get an error message 'Error writing to target file! /storage/emulated/0/Download/DSC3948.NEF!

Any suggestions would be welcome.

I'm not the author of the USB Stick plugin, so I can't say what's wrong. You should try mailing the author.
Also if the stick is formatted with FAT32, you may be able to access it without plugin via "Add custom location" in the home folder.