Have you seen Product Update - What you need to know?
If any errors appear for installed solutions, then the solution package upgrade failed. To resolve the error, click the solution and then click Deploy Solution. This should deploy the solution. If not, reset IIS (Start->Run->IISreset) before clicking Deploy Solution again. Resetting IIS resolves this issue as it releases all locks on the application files. After deploying manually, reset IIS on each front end server.
If the release notes indicate that a database update is required, do the following.
Click Update database version.
Note: If you receive an error when attempting to access Nintex Administration page, ensure that nintexcommon.wsp is deployed globally. If you cannot see Workflow environment or Forms Environment sections in Nintex Administration page, ensure that nintexworkflow2019.wsp, nintexworkflow2019core.wsp, nintexforms2019.wsp, and nintexforms2019core.wsp are deployed globally. To view deployment status, on the Central Administration Home page, click System Settings, then click Manage farm solutions in the Farm Management section. See Deploy the solutions in the installation guide for information on the deploying solutions. (Note: The deployment option “All content web applications” does not include the web application.) No IISrest is required for deployment to the Central Administration web application.
On the Central Administration Home page, click Nintex Administration and then click Database management under Licensing and setup.
If a database update is available, it will be indicated in red with an option to Update database version.
If the external platform has not been enabled, see the following installation guide pages for more information.
For instructions on accessing the Services snap-in, see the Microsoft article Services.
Right-click SharePoint Time Service and select Restart.
(Optional.) Upgrade from Nintex Forms to the Nintex Forms Enterprise Edition