iPad mini Smart Cover stopped working

The Smart Cover (the official one) worked as expected on my ipad mini for about 5 weeks after which it stopped working, in the sense that the ipad no longer wakes/sleeps when opened/closed. I have double checked the setting that turns this feature on/off and it is indeed turned on. I have also tried a hard reset and a factory reset. With the later I tried the cover before restoring my backup in case it was related to something in the software stack installed. Even then the Smart Cover was no longer working.

Is this a known issue? Do the smart covers themselves tend to have malfunctions/errors that prevent them from working?