M390 is an extremely hard steel.
It was hard for me to believe, but these old standards, won't get modern steels sharp.
When knives were made only from 420, 1055, or 1095, (or 440B) I could create a good edge with these abrasives. And then, modernity hit! To set the bevel, I have to use coarse DMT diamond stones. I use the 8 inch versions and I of course, use the absolute most essential item I have to sharpen a knife, the Swiss Army knife magnifying lense:
If you cannot see what you are doing to the edge, you won't be sharpening the knife! With that magnifying glass I can see if I am creating one flat bevel, per side, and I can see if the edge is centered in the blade. Both of these particulars are critical to sharpening. And, I can see the burr on the edge. At some point, using a coarse diamond stone, my bevels are flat and even, the edge centered. And that is when I finish the edge with one of those traditional "soft" stones. I use them to rub the burr off. I feel for the burr, find which side of the edge it is on, and lightly use those "soft" stones, to knock the crest off, so to say. Once the edge has the same drag from both sides, I am done.
One of these days knife blades will be harder than diamond, and then sharpening them will be an impossibility. You think diamond is the hardest substance, well, times change. They will create a new cross that knife sharpeners will have to bear.