No I2C ACK from Honeywell HIH-6120 humidity sensor
It looks like it's ACK'ing fine to me but maybe or the code is interpreting it wrong?

I see the 0x27 (data latched on the rising clock edge), and then the read/write bit is 0 meaning you are doing a write, then the slave drives SDA low to indicate an ACK. You can see right when it happens there's a tiny step down to exactly 0 Volts.

Then on the falling edge of the clock the slave is releasing the SDA line (as it should) so the SDA rises up, then the master is taking over the bus and driving SDA line low. That's why you see that narrow blip.

So it looks fine. Somehow the HW is interpreting it wrong or your understanding of the API might be wrong?