Possible Sweat Gland Damage After Laser Treatments

Laser resurfacing leaves dead skin cells and debris on the skin after treatment. This debris coupled with swelling of the skin can block sweat glands and oil glands and can lead to acne outbreaks and milia, dilated sweat glands.
Good skin care can solve this problem. Microdermabrasion helps.
This is a temporary phenomena and will resolve as you heal.

Dr. Goldstein has explained the anatomy in a pertinent, clear and succint manner.
This is most unlikely to last. The sweat glands are located at a level at which any significant injury would incur scarring.
If you have healed uneventfully from the laser then it is not likely you sustained any additional damage.
Is it possible you underwent Botox treatments to the forehead around the same time. Some physicians like to pretreat with Botox to relax the wrinkles and allow more effective response to the laser treatment. Botox is known to stop sweating and this your lack of sweating could be related more to that than the laser treatment.

Laser treatments typically only penetrate the first few layers of skin. Depending on the type of laser and the specifics of your treatment will vary the depth of your treatment. Most "resurfacing" or "fractional resurfacing" laser treatments penetrate relatively deeply into the dermis and are called "ablative therapy" because they are actually causing some degree of tissue destruction.
Sweat glands are typically in the very deep dermis or hypodermis and have channels that penetrate through the dermis and epidermis to allow sweat out when signaled by the underlying nerves.
As the sweat glands and nerves that supply them are deeper that a typical laser treatment should be able to penetrate they are likely still intact.
Hope this helps.