(a) A group accident and health insurance policy must provide that written notice of a claim must be given to the insurer not later than the 20th day after the date of the occurrence or beginning of any loss covered by the policy.
(b) Failure to give notice within the time prescribed by Subsection (a) does not invalidate or reduce any claim if it is shown that:
(1) it was not reasonably possible to give the notice within that time; and
(2) notice was given as soon as was reasonably possible.