The label is obviously missing in the resources.
You can add it following these steps:
- Navigate Administration > Labels & Messages
- Create new label
- Fill the required fields as in the attached image
- Restart the application
If you have any additional questions, do not hesitate to contact us.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items