Make visible the article in Draft and Needs Review mode to other members of the community group
Is the below permissions checked from permission tab ? If it's not then set the below permissions:

Workbench Moderation:


View all unpublished content
View the moderation messages on a node
View moderation history
Use "My Drafts" workbench tab
Use "Needs Review" workbench tab


Also let me know which version of workbench moderation module you are using .