First, check whether more than half of the servers start zookeeper. If yes, use the JPS command and find that the quorumpeermain main class is not started

[atguigu@Hadoop103 zookeeper-3.5.7]$ jps
14850 Jps

The most likely cause: Zookeeper decompression path in the conf folder zoo.cfg (I am here after changing the name) configuration when adding the content after the addition of a space and the creation of myid up and down there are empty lines or left and right spaces, enter the file deleted, and then check the jps

#######################cluster########################## 
server.2=hadoop102:2888:3888 
server.3=hadoop103:2888:3888 
server.4=hadoop104:2888:3888