Deduction u/s 80p

I have filed return for A.Y. 2013-14, 2014-15, and 2015-16 of co-operative housing society claiming deduction of Rs.50000 under section 80P, But the deduction was disallowed and demand has been raised without disclosing the reason of disallowance.

However, the same deuction was allowed in A.Y. 2016-17 and no demand hass been raised.

Guide me about the reason of disallowance for the earlier years.