I used an old oil base primer to prime windows. After two day the primer is still soft, and scratches easily with a finger nail.
What should I do?
Allow the primer more time to dry. Standard oil based wood primer can take a few days to dry. For future reference; You can add a special drying/curing chemical called Japan Dryer to oil based primers and paints. Japan Dryer speeds up the curing of these coatings.
Slightly soft oil based primer will cure under the paint and shouldn't affect the final outcome. In this situation I allow a couple more days of drying time and then go ahead and paint.