Ambari 2.2 to 2.4.0. update

[jankytara]

Hello,
 
I updated Ambari 2.2. to 2.4.0. During installation there were no errors, I 
sucessfully update schema of database and started server/agents. After login to 
webUI, there is operation Check Host with sub-task Check Host Actionexecute 
which is stalled. What does this process mean?
 
Thank you
Jan