ALTLVDS pins io standard

I found the reason, why Quartus doesn't accept your design.

You connected four RxLVDS instances to the same pin. This doesn't work, because Quartus needs to implement the double data rate registers as IO registers. So there can be only one RxLVDS MegaFunction for each pin.

P.S.: You can disable the requirement to use IO-registers by removing the Altera synthesis attributes LVDS_RX_REGISTER=LOW and LVDS_RX_REGISTER=HIGH from RxLVDS_lvds_rx.v, which resides as a copy in the db directory. Then Quartus can use regular LE registers, but the timing will become worse, of course.