I have the same issue with the WorkCenter 6515 using Mojave or Catalina. Scan works on my old mac that uses macOS High Sierra.
There is a new ICA Scanner Driver available, but only USB. https://www.support.xerox.com/support/workcentre-6515/downloads/dede.html?operatingSystem=macOS10_15...
I installed it, but no scan function here over Ethernet under Catalina.
I'm having the same issues. I recently purchased a new Macbook with Catalina installed and don't have the option of waiting to upgrade operating systems. The 3225 printer is a current printer model and should be compatible with curent computers and operating systems.
for everyone on Catalina:
try to install this ICA driver, my WorkCenter 3215 is now able to scan over USB. Prior to installation of this ICA driver I was getting the following error when scanning with Image Capture > 'Scanner reported an error" when saving the scanned image.