You are attempting to open up an existing case record within the Lightning Experience and encounter an error similar to the following:
This error is related to the following Salesforce Known Issue.
This error may occur if a local field (making reference to a managed package field) is included on your page layout, and the running user has not been assigned a license to that managed package.
Unfortunately, this Salesforce Known Issue is marked with a status of "No Fix," but there are a few options System Administrators can evaluate to avoid this error.
This error is related to the following Salesforce Known Issue, marked with a status of "No Fix".