Hi,
It seems that there is either no export data source or the export datasource is not active. If it exists but not activated then try to activate the data source manually (navigate to Data sources for the corresponding source system and search for the DSO name, the data source name should be 8 followed by the DSO name. Once activated then try activating the DSO.
If the export data source does not exist then right click on the DSO and chose 'Create export data source', also try replicate data source option from the source system. Then try activating the DSO manually.
Hope this helps.
Sourav
