Have you installed the Ansys Electronics Desktop as well on your workstation?
Close all Ansys applications.
Go to START > Ansys Em Suite 202x Rx > Modify integration with Ansys (run as admin) and integrate it with workbench.
Once you complete this step, launch Workbench. You will see Maxwell and other Electronics solvers in the analysis system. Drag and drop Maxwell into the workspace and then import your Maxwell project into it.