Is the manual to hand?

Is there a telephone nearby?

yes i have user manual of acs550-01

What does it say about this particular fault?

If it doesn't give sufficient information to be able to clear it, then what does it give about the telephone number of the drive manufacturer's local technical helpline?

When i switch on the ac drive, it's keypad display sowing alarm code (5001)

Repeating it here won't solve the problem!

• What does the manual say about it?
• What does the telephone helpline customer service representative say about it?

The manual says ( drive is not responding )

i am not able to contact the customer service.

Why not? Is the telephone line engaged, for example?

Is it something silly, like a damaged or loose communications cable, perhaps?

I believe that this is what's called an "unrecoverable fault", which means there is nothing that a casual user can do, you MUST contact the factory. If you cannot, then you have a boat anchor, and not even a very good one at that (depending on the size of the unit). But before scrapping it, I would take the earlier suggestion and look for a loose connection.