Chinese (hard-paste) porcelain has two properties that made it hard for Europeans to reproduce:
Chinese (hard-paste) porcelain is/was is made from a very specific mixture of minerals especially kaolinite, feldspar, and quartz. Unsuccessful attempts to replicate the mineral mixture in the 16th century resulted in the creation of "soft-paste" "porcelain" ceramics usually made from a mix of feldspars, feldspathic clays, and glass frit. Other experiments to make porcelains resulted in the invention of bone china.
Hard-paste porcelain requires a VERY high firing temperature (about 1440 deg C) to ensure the that entire piece undergoes full vitrification at the proper rate. This very high firing temperature places sigifnicant technical hurdles -- usually a special multi-stage kiln is needed that pre-heats the air before it comes into contact with the firing chamber, and often the firing process lasts several days, including warm-up and cool-down times.
The first true hard-paste porcelain in Europe was made in the German city of Meissen in 1710. The workshops at Meissen (near Dresden) were the result of a uneasy collaboration between the physicist Ehrenfried Walther von Tschirnhaus and the alchemist (chemist) Johann Friedrich Böttger. Funding for a nearly 10-year research and development process was provided by Augustus II the Strong, the Elector of Saxony and later King of Poland.