A4988 driver stopped working

Hi there!
I've been working with A4988 driver with stepper motor 17HS1538 of current 1.68A. I set a maximum current of 1.7 A using equation :Imax=2.5Vref
the motor was running with aluminium heat sink, it seemed okay as it was not getting hot to burn my fingers-I could put my finger on the sink forever and it wouldn't burn me and i used the back side of the finger.

The last time to use it was working just perfect. Yesterday I hooked up things as normal, with a 100uF capacitor across a 10A 12V power supply and all other things as required but the motor was not running, there was a voltage equals to supply's voltage across the driver outputs and the motor was getting hot but not rotating. Also there was a sound of some kind inside the motor- the sound is just what every powered stepper motor would give, not a big deal I guess.

Someone said if you pull out the wire between the motor and the driver the driver get burned. I did it quite a couple of times and the last time to do so, when I replaced the connection the driver was still working. I've been doing so and I always do so on TB6600 driver but it never burn.
I've no idea what happen and I'm just nervous I can't proceed with testing my code with two motors. The motor is perfect, I tested it on TB6600 and it was running perfectly.

The problem is the motor is not running despite everything hooked up properly. Does it mean the driver is dead? Could anyone help me please?

If you disconnected or connected the motor when the motor power was applied, you very likely killed the driver. Do not do that to any driver. If that does not kill the driver, you are just lucky.

The A4988 is good for 1A without heat sink and active cooling. 1.7A is on the edge of what that driver will handle with very good cooling.

That is one of the several possible problems.

1.7A is too much for the A4988. Its on the limit of a DRV8825 even, though that has a chance of handling it with good cooling.