Alfresco Process Services must have a valid license to work properly. Alfresco provides this license in the form of a file named activiti.lic.
Move the license file to one of the following locations:
In the classpath of the web application.
In the home folder of the user that was used to start the web container. For example, in the $USER_HOME/.activiti/enterprise-license/ folder (note the dot before activiti).
Alternatively, upload it using the instructions in Uploading a license from the User Interface.