Hello,
Click this link, https://www.support.xerox.com/en-us/article/en/x_wc7556_en-O40977, and it will take you to the instructions on how to disable/enable the energy saver mode on your WC7845. If this doesn't work, I suggest you contact our support department at 1-800-821-2797.
Recently replaced the hardrive a few days ago and reinstalled the firmware with altboot since the printer failed to boot. The printer now seems to get stuck in energy saver mode every time. Only way to get it to wake up is by rebooting it every time. Have already tried power cycling the printer and restting the GFCI with no improvement. Doesn't appear to be an option to disable the energy saver either.