iMac not scan destination on Epson Workforce 4250

You don't "disable" Airprint nor do you install the Epson drivers on an iPhone or iPad. The drivers are for Mac or PC only.

The printer is "Airprint capable," which means that devices like an iPad, iPhone or Mac that support Airprint can print to the printer via Airprint. You don't enable or disable Airprint on the printer itself.

If the suite of Epson drivers is installed and used on a Mac or PC, that does not interfere with other devices continuing to print via Airprint.

Consult the Epson 4205 User Guide. Page 112 of the Guide says the following:

Starting a Scan Using the Product Control Pane / Scanning to a Connected Computer

• You can scan an original and save it to a connected computer using your product's control panel. The computer must be connected using a USB cable or connected to the same network as your product. You can save the scanned file as a JPEG or PDF file.
• Note: Be sure you have installed Epson ScanSmart, Epson Scan 2, and Event Manager on your computer before scanning to your computer.

How is the Epson 4250 connected to your iMac and the PC? I suspect you have it set up as a WiFi printer. But is that how all devices connect to the printer ... or is the 4250 connected via USB to that PC?

You also need to have (and be using) the full Epson drivers on the iMac. If you are using Airprint, in my experience that explains why you cannot scan TO the iMac. You need the Epson Event Manager on the iMac (part of the full Epson driver set) in order to use the control panel on the 4250 with the iMac. (You may also need to use a wired USB connection between the 4250 and the iMac.)

ISTR, that the button only works with PC's not Macs, since the computer has to constantly talk to the printer to see if the button is pushed.

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and try to scan to your Desktop or wherever you want. Reboot normally and try again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.