Data re-import: One or more of the option value for the pick list are not in the range of the allowed. After Upgrade from Dynamicsc CRM 2011 to 2015

After a recent upgrade from Dynamics CRM 2011 to 2015 I get the following error when trying to re-import data into CRM.

'One or more of the option value for the pick list are not in the range of the allowed'

This happens for all entities even if the exported to reimport excel file does not contain any columns which are option sets. If i dont even update the data i get the error regardless

Has anyone experience this issue.

Thanks in advance Gman