Usually for the first time, it would take about 30 seconds for the water to flow through. If you have waited this long but no water is coming out, your cartridge may have been placed upside down.
The gold media, which is KDF-55, should be pointing at the sitting once your filter is sitting again on your counter. Please check again to see if the cartridge is installed properly.
If your cartridge is in upside down, your water would taste strange as well.