Upgraded my Apple 27" to 11.4. My Epson Stylus Photo R2400 will not show up. Downloaded new prnter software, still nothing.

Go to the Epson Support page for this printer,

https://www.epson.co.uk/products/printers/inkjet-printers/photo/epson-stylus-photo-r2400/Support-Downloads

Make sure the operating selector is set for macOS 11.0 Big Sur, under Drivers & Software click on the + buttons

to reveal the downloads available for you.

Hello,

Did you also install the 10.85 printer driver?

https://www.epson.co.uk/support?productID=1440&os=38#drivers_and_manuals

If necessary, try resetting the printing system and re-adding the printer.

Reset the Mac printing system to solve a problem - Apple Support

Add a printer on Mac - Apple Support