The answer to 'flat roof damage' is that there are several common causes, including poor drainage, age and wear, and damage from weather or debris. Symptoms can include standing water, cracks, blisters, or leaks. Solutions may involve patching, coating, or full roof replacement, depending on the extent of the damage.
For minor issues, some DIY repairs may be possible, but it's generally best to have a professional roofing contractor inspect the roof and provide a recommendation. Attempting major repairs without proper expertise can lead to further damage or safety hazards.