I am unable to wake up for Fajr Salaat.

Answer

We are not aware of your lifestyle, hence cannot provide reasons. Nevertheless, reasons for inability to wake up are numerous, e.g.

Kathaafat (spiritual heaviness, density, lethargy) caused by darkness in the soul which is the result of sinning and indulging in futility.

Overeating

Pride

Gheebat

Cruelty to the wife

Not guarding the eyes from haraam glances

Neglect in fulfilling the rights of others.

Examine your life style and make amends to reform.

May Allah Ta'ala grant you the taufeeq to wake up in time for Fajr Salaat. Before going to bed, make wudhu, perform two raka'ts Nafl, recite Istighfaar and make dua.