Will a Muslim's reward be lost and their deeds not be accepted by Allah if they repeat their adhkar and supplications without contemplation?

The acceptance of acts of worship is a matter of the Unseen. The one engaged in remembrance (dhikr) should reflect on the remembrance and feel the greatness of Allah so that both the heart and tongue are occupied with it, and the reward is complete. The one who remembers with their tongue without reflection is rewarded for the movement of the tongue, because "the movement of the tongue with remembrance, even with heedlessness, earns reward, for it is better than the movement of the tongue with backbiting; indeed, it is better than absolute silence." The remembrance of the one who reflects on the meanings of what they are remembering is more complete, but the confirmation of the reward for acts of remembrance does not depend on reflection and understanding.