Just to end this thread. When I replaced the yellow toner everything went back to normal. So lesson learned. When you are out of toner, this printer will NOT go into any sleep or power-saving mode. Thanks for the help!
Further to my first post, another fact is that the printer is telling me that it is now out of yellow toner. When I tried to manually put the printer into sleep mode it said it could not and gave I think 3 possible reasons, one of which was due to a fault.
Is being out of toner considered to be "a fault"? I guess it must be. When the new toner arrives I will circle back here and give an update.
My Workcenter 6515 always went into power saving mode exactly the way it should.
Today I replaced the CYAN toner with a non-Xerox toner and immediately power save mode stopped working.
The printer prints fine, but simply will not go into power saving mode. The only choice I have is to do a complete power down cycle.
Please advise how I can fix this.
Total impressions 5265
Activation Date 05/14/2021
Software versions - system v65.65.51 Controller ROM v1.77.0 Boot ROM v11.1.219
Printer is connected by USB and is not attached to ethernet or wifi.
PC OS is Windows 10 x64