Most likely there is an issue related to the stored credentials (particualary those stored as the default credentials within the program options). Typically, when this is the issue, you will receive an error when attempting to launch the console.
You can clear the default stored credentials for all users by running the following query against the NetChk Protect database:
DELETE FROM credential where (type=6)
If this is resolves the issue, we recommend either using a single, unique user credential for each console machine, refraining from storing any default credentials, or upgrading to our 7.8x release.
This is a known issue in the 7.6 + 7.8 in regards to having multiple consoles and multiple users. In the past you could have a service account for all consoles and any admin would be able to access any console to perform scanning, deployment, and reporting tasks. With the 7.6 + 7.8 builds the console, when using saved default credentials, can only be accessed by those very same default credentials. This negatively impacted our users and we have corrected this issue in our upcoming release.
There are two options to approach this issue.
Do not save the creds on either as default. Otherwise console A would be only accessible by user A, console B and user B. Console A could never be accessed by user B, and vice versa. In this configuration any user may log in to any console and will be prompted to add credentials when deploying. Credentials still may be stored in the machine groups.
Otherwise you can create a user account for each console and have that as the only account that accesses it. Same example as above. User A can log into console A, User B can log into console B. User A cannot log into console B and vice versa. Repeat out for more than two consoles.