Even after 44 days of hair transplant surgery, my scalp feels numb. When will it regain sensation?

It may take weeks to months before the numbness goes away.  Everyone is different.  If you are concerned it is best to contact your doctor.

you didn't mention which part of the scalp(donor v recipient) or which method(FUE v strip). Either way it is not uncommon to have a numb feeling for several months due to temporary nerve injury.

Numbness in the recipient area following a hair transplant is normal.  Superficial nerves branches that innervate the skin can be injured during the recipient site making process.  However, this injury is usually not permanent and those nerve endings will recover and once again provide sensation to the scalp.  Recovery time is different for every person and can take 6 months to even a year for full sensation to return. Be patient!  As always, if you have further concerns please contact your surgeon to discuss.
Best regards,
Dr. Phipps