I2C works with UNO R3, but not with XIAO

I’m connecting to a Sensirion SDP3x differential pressure sensor, using the Sparkfun library. It works fine when I compile for Uno R3, but when I compile for XIAO, it won’t connect to the sensor. I have tried 2.2K and 4.7K pullups. Is there something that I have to do differently with a XIAO to make I2C work? I am seeing activity on the I2C bus.