Creating Least Cost Path with cost distance analyse

I’m trying to create Least cost Path analyse between two points in QGIS. I had DEM and from this I created Slope with various elevation values. Then I made two points with different layers. Both of them include only one point. When I want to run Least cost path algorithm, it appears problem starting point is no legal point, Then I changed the points but its same. Could someone help me with this issue?