Arduino Uno to ATtiny44A I2C communication
This is a pitfall of using the Arduino Library - everything is so abstracted from you that a little hiccup and you're completely lost. I don't know much about the Arduino libraries, but if it were me I would enable and use the TWI/I2C interrupts and see if they are being triggered. A simple LED blink inside the ISRs would do just fine as an indicator if it's working properly. If the LED doesn't blink then then problem lies in the protocol implementation.

Are you connecting the SCL and SDA correctly between the controllers? And do you have the SCL and SDA lines tied to pull-up resistors to VCC?

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