I implement the 10GBase-R protocol on the transceiver native phy. I use a reset controller in the my project. After power-up or reset, rx_is_lockedtodata in not asserted and my receiver in reset state always. Arria 10 GX
As I understand it, you observed that the rx_is_lockedtodata signal of the A10 Native PHY is not asserting. For your information, the rx_is_lockedtodata not asserting indicates that the CDR is unable to achieve lock to incoming data.
The following are some of the general causes for CDR unable to achieve lock for your reference to look into:
You can try to look into the above areas to see if can spot any anomaly.