ANCS does not piar after deleting bond information in iphone.

I'm testing with pca10028, ASCS(SDK11.0.0) example and iphone.

But pca10028 does not piar after deleting piaring information in iphone.

"[DM]: !!! Bond/key refresh !!!" message appears.

Then when I enter sleep mode by pressing button 1 and delete bond information in pca10028 by pressing button 2, it's paired again.

why is this happenning??

Why can not pca10028 recognize new device right after I deleted bond information in iphone(not, pca10028)?

I think pca10028 should recognize as new device because IRK distributed is changed.