Why toner cartridge shipping seals are important
When a new toner cartridge is opened for a printer, it should have a shipping seal. This is usually a strip of plastic that is wrapped around a main roller in the cartridge. It will have a little tab sticking out from the cartridge. Prior to using the cartridge, this tab must be pulled, thus removing the seal. Otherwise, the toner will not come out and your prints will be blank.
Just as it is important to make sure a jar of peanut butter has a proper seal before it is opened, a toner cartridge must have a seal. If the seal is lacking, return the cartridge for a replacement. The seal wraps around the main roller in the cartridge which creates a gap between the application rollers, developer and doctor blade. This prevents any toner from being released and allows the cartridge to be shipped. If the seal was removed or there was a problem installing the seal during the manufacturing process, you will immediately know because laser toner powder will have dumped out into the plastic bag during shipping.
Another problem that is common with the seal, you are unable to pull the seal out of the cartridge. I have seen this issue happen on a number of occasions with brand new genuine HP toner cartridges. If the seal is jammed, do not continue to tug on the seal. Instead, immediately call to get a replacement cartridge.