IPv6 completely locked it up. It would reboot over and over. This happened after changing my home router to one with full ipv6 support. Disabling ipv6 on the printer fixed it. It could be that subsequent firmware updates fixed this but I haven’t checked.
I use only genuine HP toner. No way I am trusting random toner from the flea market—er, Amazon.
HP Color Laser Jet MFP 281cdw