if you enable the hierarchy setting for this relationship, all rollup definitions that use the existing hierarchy will become invalid. Do you want to continue?

while creating and configuring Hierarchy in MS CRM 2015, if you get the below error...
 "if you enable the hierarchy setting for this relationship, all rollup definitions that use the existing hierarchy will become invalid. Do you want to continue?"

 

Check that you have already a relation that has been declared as Hierarchy.

by rule you can have only one and self relation hierarchy.

so use that in case create  a new....

 

hope its helpful.

 

Regards,

yes.Sudhanshu