Execute Task (Export Web Map Task)

Unable to complete operation.
Error executing tool. Export Web Map Task : ERROR 000590: WebMap_as_JSON is empty. Web map has invalid JSON. Failed to execute (Export Web Map). Failed to execute (Export Web Map Task).

Web Map as JSON: (GPString)
Format: (GPString)	PNG32
Layout Template: (GPString)	MAP_ONLY
Options:
Output Spatial Reference:
Process Spatial Reference:
ReturnZ:	True False
ReturnM:	True False
Return True Curves:	True False
Return Feature Collection:	True False
Context:
Format: