1. You need to enter at the transmission point in Sumeru City. The transmission anchor point is on the left hand side of sumeru city. After entering, you must enter through the two doors of Fatwa Courtyard to find Jingshan Palace.
2. At present, Jingshan Palace has not been opened in Genshin Impact Games, and the current version of Jingshan Palace map has not been made, so it is impossible to enter Jingshan Palace in Sumi City.
These are the reasons why Jingshan Palace in Sumeru City can't get in. I hope it will help solve your problem.