I have created a PCB with the reference design from the data sheet. Although the chip wakes up and can communicate through the I2C, I cannot get it to power up the supplies. When PWRUP is pulled high, the oscillator begins running for the negative supply, and I see about -2 volts on VN with a meter. The chip then shuts down and asserts either VCOMF or VN_UL. The VCOM pin is tied low to disable it.