Ir refund not received tet

I have filed a revised IT return for FY 2017-18 in Aug 2018 for a mistake in the TAN number of the TDS deductor.  This is after I got 143(1) and filed the return under 139(5).  I am yet to get my refund although it's more than 5 months.  Due to the delay I filed a rectification which was rejected as the revised return is already under process.  Please let me know what action I should take to get my refund.  All the reply I get from CPC is that the return is under process.  Please help.