Carry forward losses if shifting between new and old tax regime

hi, I understand that salaried employees can switch between new and old regime tax slab every year.
suppose if a person
opts in new tax regime in first year n doesn't claim carry forward losses of earlier years
in the next year if he opts out of new regime and chooses old regime can we claim the carry forward loss of old years?
basically what happens to cf losses when shifting from old to new and new to old