instance in cloud service keeps unhealthy

Hi team,

We have a cloud service that deploy our production environment in East US Azure data center. 

From 4.30 the instances keeps 'Waiting for the status (Role cannot be reached by the host system.)'

and 'Busy (Stabilizing role... Calling OnRoleRun. [2015-05-01T01:39:35Z])' 

we tried to image these unhealthy instances but it doesn't work.

we would like to know how can we fix these problems, any feedback will be appreciate. 

thanks in advance.