Input or output missing root element error
When a mapping uses an input or output root document element that can no longer be found in the input or output schema it results to input or output missing root element error.
This could happen if you edit or change a schema or when you import a mapping with inconsistent metadata. In the case of inconsistent metadata, check the mapping.input/output.element
from the mapping.properties file and verify that the values are correct. You can manually edit the values and try to open the mapping again.