NEMA 34 Stepper Motor Upgrade Issue

[Martha]

Hello everyone,
I decided to upgrade my NEMA 23/425 motor to a NEMA 34 motor. Thinking the upgrade would be simple, I ordered a new motor and installed it today. However, since installing it, my machine has been stuck.
I'm using a DM856 driver connected to a 48V power supply. Before replacing the driver, I could easily run at a slow speed of 8000 mm/minute. Now, I'm stuck at 500 mm/minute. The acceleration is set to 50...the number of steps hasn't changed. The machine has a 1605 ball screw.

Here are the new motors:
34HS59-5204S and 34HS46-5204S all comes from oyostepper website.
I feel like I'm missing something, but I can't quite put my finger on it...
I currently only have one motor connected to the X-axis...
If I run it too slowly, it seems to get stuck.