Nintex icons are missing from Central Administration.
The Central Administration feature is not activated. It's possible that the Nintex Workflow or Nintex Forms solution was deployed to the front-end web servers but not to the server hosting SharePoint Central Administration.
To resolve this issue, deploy the Nintex Workflow and Nintex Forms solutions to the Central Administration Web application; if needed, activate the relevant Nintex features manually using Stsadm commands.
To deploy the solutions to Central Administration
On the Central Administration Home page, click System Settings.
In the Farm Management section, click Manage farm solutions.
The Solution Management page appears. Solution deployment status is indicated in the Status column; the Web applications to which the solutions are deployed are indicated in the Deployed To column.
Deploy the Nintex Workflow and Nintex Forms solutions to the Central Administration Web application:
Display the Deploy Solution page: Click the solution that you want to deploy and then click Deploy Solution.
In the Deploy When? section, select Now.
In the Deploy To? section, select the URL for the Central Administration Web application.
Click OK.
To activate Nintex Workflow features on Central Administration
Run the following command, where http://centraladminurl:port is replaced with the URL and port for the Central Administration Web application.
stsadm.exe -o activatefeature -name nintexworkflowadmin -url http://centraladminurl:port
To activate Nintex Forms features on Central Administration
Run the following command, where http://centraladminurl:port is replaced with the URL and port for the Central Administration Web application.
stsadm.exe -o activatefeature -name NintexFormsAdminWeb -url http://centraladminurl:port