Arduino Uno (master) and ATTiny85 (slave) I2C connection not working
I modified your Uno sketch slightly to add a delay:

#include &lt;Wire.h&gt;

#define SLAVE_ADDR 0x50

void setup()
{
  Wire.begin();
  Serial.begin(9600);
}

void loop()
{
  Wire.requestFrom(SLAVE_ADDR, 1);

  if (Wire.available())
  { 
    byte byteReceived = Wire.read();
    Serial.println(byteReceived, DEC);
  }

 delay (1000);
}


Upon testing, it worked perfectly!



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I suggest a wiring error. Check you have:

Uno    ATtiny85
--------------------
A4      pin 5  (SDA)
A5      pin 7  (SCL)
+5V     pin 8
Gnd     pin 4