Arria 10 DDR4 EMIF IP Calibration Failure

So you say that you've taken the HPS out of the equation by creating a standalone design, which is good. But is the standalone design your own design or are you generating the example design project from the EMIF IP parameter editor and using that design straight with no alteration (other than assigning to the appropriate I/O banks to connect to the external memory)? If it's not the example design, try the example design first and see if you're getting the same results.

If it is the example design and you're still running into issues, a good sanity check is to check your parameter settings one by one against the external memory requirements from the external devices specifications. It may seem tedious, but there are so many settings, it's very easy to make a mistake that prevents even basic operation of the interface.