Hello
You will need to allow ESET Security product to access the user protected date on the client with macOS Mojave. Without this permission, ESET product will not be able to scan some folders. User protected data is a new security feature introduced by Apple in macOS Mojave. Go to Apple menu -> System Preferences -> Security & Privacy. In the Privacy tab go to Full Disc Access and add your ESET Security product there (You can drag and drop your ESET product to the list)
You can find information also in this ESET Knowledgebase article: https://support.eset.com/kb6971/