Make an SSH connection to the server running the API Gateway and select 2) Display CA API Gateway configuration menu.

Welcome to the CA API Gateway - 9.3.00
running on Red Hat Enterprise Linux Server release 6.10 (Santiago)

This user account allows you to configure the appliance
What would you like to do?

 1) Configure system settings
 2) Display CA API Gateway configuration menu
 3) Use a privileged shell (root)
 4) Change the Master Passphrase
 5) Display Remote Management configuration menu
 6) Manage HSM
 7) Display CA API Gateway Enterprise Service Manager configuration menu
 8) Display Patch Management menu
 9) Display Log Viewing menu
 R) Reboot the CA API Gateway appliance (apply the new configuration)
 X) Exit (no reboot)

Please make a selection: 

Select 7) Manage CA API Gateway status.

This menu allows you to configure the CA API Gateway application
What would you like to do?

 1) Upgrade the CA API Gateway database
 2) Create a new CA API Gateway database
 3) Configure the CA API Gateway
 4) Change the CA API Gateway cluster passphrase
 5) Delete the CA API Gateway
 6) Display the current CA API Gateway configuration
 7) Manage CA API Gateway status
 8) Reset Admin password
 X) Exit menu

Please make a selection: 

If the status is RUNNING, this means the appliance is considered to be in a stable state.

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CA API Gateway Status
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Configuration:
    Node Status = RUNNING
    Node Status Timestamp = 2020-07-14 05:19:56
    Node Status Since = 2020-04-08 08:55:26

Press [Enter] to continue.

If the status is STARTING, this means the appliance was probably restarted moments ago and is still in the process of starting up.

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CA API Gateway Status
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Configuration:
    Node Status = STARTING
    Node Status Timestamp = 2020-07-14 05:57:01
    Node Status Since = 2020-07-14 05:56:26

Press [Enter] to continue.

If the status is WONT_START, and the appliance was restarted moments ago, you should simply wait a few moments and then check the status again. If the status remains WONT_START, you'll have to check the logs to determine what the issue is.

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CA API Gateway Status
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Configuration:
    Node Status = WONT_START
    Node Status Timestamp = 2020-07-14 05:19:56
    Node Status Since = 2020-04-08 08:55:26

Press [Enter] to continue.