check that the reset pin is set to logic low. Tying it to ground is good enough if you don't intend to use it in your circuit at all. Tying it to +ve is a bad idea, since +ve resets the device, and sends many pins to high impedance state.

Also, make sure the oscillator driving the microcontroller works. Without some kind of oscillation, instructions will not be able to execute.

Make sure your power supply works. Have you tried running the circuit with a 5VDC power adapter?

A simple test for your power supply is to connect an LED and a resistor in series. The cathode goes to -ve, and the anode goes to at least a 500 ohm resistor. The other end of the resistor goes to +ve. If the light does not come on, then your power supply needs to be replaced.

For your microcontroller, you need +12V applied to the VPP pin to enable the programming of it.

Also, check your datasheet.

If all else fails, try another 89c2051.

chips can fail to work too.