Rstamp6

Hello all. My dad has a 2017 Fusion with the 1.5l ecoboost. Today when he went to leave for work his car wouldnt start and would just crank. While it was cranking it sounded like it was backfiring. Does anyone know what could possibly be the issue? The coolant was low last week so he topped it off and today it looked normal. Theres no codes or anything. oil was normal. Havent pulled the plugs yet but figured I would check here to if anyone experienced anything similar.