Context: I have placed this part on a new design. I have a dev kit as well. A failure to start switching problem is duplicated on the dev kit that is setup in the default state (as sent by ST) for use in buck configuration, targeting a 4.2V float LiPo battery.
Failure scenario: I have for the test a bench supply set at 8V with a 1K resistor in series to simulate a higher impedance src. What I observe in a stone cold bootup situation that the PVin + node is basically shorted or held in fairly low impedance for some time - even minutes! Then suddenly with no external changes, it releases the low impedance and begins switching making the 4.2V. Once this begins, I can cycle src power and it starts up readily. If I let it sit OFF for some considerable time (like overnight) THEN I can again reproduce this failure to start scenario. It seems to self-heal, but takes time. In one instance, I connected a battery simulator (set at 3.6V) to the Vbatt node (CN2pin1) and it started switching at once - making 4.2V as desired.
Risk:
1) This is a show stopper as it happens with or without the battery connected as noted.
2) Lastly a note in the datasheet Fig 3 seems to be touching on a related reset trouble but for the life of me their explanation of how quasi-shorting the Vbat to the Store fixes the problem escapes me. It may or may not be relevant to this problem.
