The qianlong emperor rejected lord macartney's request to establish an embassy in china because:

Basically it was different world views, which were incompatible with each other, because the Chinese Empire of that time, did not allow other countries to have embassies in China. Count George Macartney, directing the British delegation, did not achieve his main objective of initiating trade with China; a secondary problem was the lack of commercial concessions that China gave to foreigners. Emperor Qianlong then sent a letter to George III, giving an explanation of why, he didn't allow an embassy in China. History tells us that Qianlong's refusal meant a missed opportunity for China to achieve a first agreement with the West. This failure continued to affect the entire Qing Dynasty, which suffered from foreign pressures and internal conflicts.