Nintex Promapp Viewing Permissions on a Group may not be applied immediately.  

There is a background job that runs every time viewing permissions are set up.  This job goes through and sets up the permissions for each user.  

If there is a backlog of background jobs, or you have a high number of users, this may affect how long it takes for this to run.  

Please contact support@nintex.com if it seems to take too long, and we will investigate further.