2018 Mac Mini won't go into internet recovery mode
I am trying to reinstall an operating system onto my 2018 Mac Mini so I can sell it on eBay for needed money to help me pay for needed counseling services and needed speech language therapy. I already tried shift - option (alt) - command (Ctrl) - R and command (CTRL) - R to no luck. Every time I turn my 2018 Mac Mini and GeChic 1503H 15.6" Portable Monitor on my 2018 Mac Mini tries to go into internet recovery mode by allowing me to connect to my parent's AT&T internet connection. After a while of trying to connect to the Internet I get a message apple.com/support -2003F. I also think I deleted the operating system and I can no longer get an operating system onto my 2018 Mac Mini at all. I also have found out the 2018 Mac Mini will not allow me to install a new operating system using my flash drive (where I made a bootable version of Catalina OS on it) plugged into the 2018 Mac Mini. Any help will be appreciated on new ideas I could try before contacting Apple Support about this would be appreciated.