Are there signs for the acceptance of fasting or any voluntary act, especially with the repeated failure to wake up for Fajr prayer on fasting days, and is this an indication of the non-acceptance of the act?

The questioner is advised to rely on trusted interpretations or reliable scholars regarding their Qur'anic reflections, and not on mere personal opinion. Not waking up for Fajr prayer on fasting days does not indicate the non-acceptance of the fast; it could be due to ordinary reasons or satanic whispers. If one takes measures to wake up but fails to do so, there is no sin upon them. A Muslim should not despair of the acceptance of their acts of obedience, and it is sunnah for them to hope for acceptance. The acceptance of acts of obedience is a matter of the unseen, but one of the signs of accepted good deeds is being granted success to perform another good deed thereafter. Therefore, it is advised to persevere in fasting and acts of obedience and not abandon them on the pretext of not waking up for Fajr or feeling that they are not accepted.