Hi,
Don’t know the monitor but searching online seems to suggest that the backlighting is provided by a CCFL tube and not LEDs.
If this is the case it could be that the inverter power supply has failed or perhaps the tube itself.
Couldn’t find a schematic for the monitor which would help to check the inverter circuit, but if it is determined that the CCFL tube (aka lamp assembly) is the problem I found this [http://h22235.www2.hp.com/hpinfo/globalcitizenship/environment/productdata/Countries/_MultiCountry/disassembly_monito_201041519166.pdf|guide] that shows how to remove/replace it in a HP2509 monitor. I realize that it is not your model but it may be close enough to be of some help.
Here’s a link to a CCFL [https://www.ccflwarehouse.com/cclawiwi.html|supplier] that may also help.