Why will GIMP not read a jpg file ?

[Ronald Walker]

Hi, I am running Gimp 2.10.38 on a PC running UBUNTU 24.04. Gimp is on a SSD with the other apps and my photographs are on a 2Tb HD with other data. When I try to open a photograph in Gimp, it recognises it but says "Reading permission denied" I can open the file which is a jpg in other programmes with no problem. I put one of the photographs on to a USB stick and checked the properties which included permission for read and write. I tried to get Gimp to read it but got the same response. I tried the USB stick on another computer running Windows 10 and Gimp on that PC accepted the file with no problem. What am I missing here ?
Ron.