Due to the electricity was suspended a couple of days which to effected the factory's production. We cannot deliver the goods for 19 June. Would you please ask the customer to postpone the delivery again to 24 June but waive the penalty?
I'm confused. Was the electricity failure for two days or two days ago?
Who is making the delivery - the factory or the customer?
The original delivery date was meant to be 19th June? The new delivery date is 24th June?
Why are you asking the customer to postpone delivery? Surely you are postponing delivery! And you're also asking the customer to waive the penalty? What penalty?
I'm going to take a guess at the points above for the moment, and have amended your paragraph thus:
Due to the power failure two days ago/Due to the recent power failure which lasted two days, and affected production at the factory, we will be unable to deliver the goods on 19th June.
Please ask the customer if a new delivery date of 24th June is acceptable. Please also request that they waive the "late delivery" penalty.