There are two types of screen used in some laptops.
The first is a LED back light source.
And the second uses a white cold cathode tube arrangement.
If the laptop needs a Inverter then it is the latter of the two.
How ever not all cathode based sealed units run on the same power provided from the motherboard of the laptop. Plus the inverter must be exactly the same as the old one used.
Was the screen an ebay buy ?
Double check from the motherboard to the inverter board. that the pink and white wire are attached to the other end of the inverter board coming from the new screen. The type of inverter matters.
so if it was bought separate from the new screen it could be the problem as the actual voltage it requires is not right for the motherboard supplying it.
The wires not connected, or the wrong type of inverter board power requirements are often the cause of no back light with a cathode back light array.