Epsonscan 2 not working with a regular user (non-admin or not in the sudoers list) on Ubuntu 20.04LTS

my father's notebook runs Ubuntu 20.04 LTS. There are two users: me as Admin (with sudo privileges), my father who plays a Standard (aka non-admin, non sudo priviles) user. He recently bought an Epson printer (ET-2785) and I have just installed the Epson Scan 2 utility; I noted the following issue: when I am logged in with my user and launch the Epson Scan 2 application through the classic 9-dot of the Gnome interface, it opens up and I am able to configure the scanning settings (output folder, dpi, quality of scan...) and start the scan; when he is logged with his credentials the Epson Scan 2 does not show up and I cannot understand if it is locked, failed or so. Please, consider that I do not start the application with the sudo command in the terminal, but I launch the application as any other software program, by clicking the application icon. The printer/scanner is seen by WiFi network, because I was not able to get the USB working (this is another weird issue). I looked already in the official user manual but nothing is mentioned about the matter. Was anyone in the same situation and was able to fix the problem. I strongly need some support. Thank you very much.