For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
When I bought the LIO from ebay it came with a new flex. Well, connector looks fine on both sides (under scoope). there is no signs of liquide anywhere. Not sure what to meassure.
Check if voltage from pins 7 & 9 of J4700 arrive to LIO board.
Be sure HDA_RST_L stays high.
Also check resistance to ground (diode mode) on all HDA_ lines...