Axes no longer home/move

I used an oscilloscope to check the step and dir signals, nothing going through. Is there a way to verify those ICs are the issue, or do you just know they are the most likely failure point?

If you don't have ~5V absolute between STEP+/DIR+ and STEP-/DIR- (0 ..3)
when unloaded, that means the U5 or U7 (or both) are bad. This is because say STEP0+ and STEP0-
are inverted  copies of the same signal, so regardless of signals further back, there should
always be ~5V (no load) between them.

Also U7 show obvious signs of overheating. Typical reason for this is accidental connection of the
step/dir signals to a voltage outside the 0 to 5V range.

You might check the STEP- and DIR- pins to see if U5 is OK
 

I checked every STEP-/STEP+ and DIR+/DIR- pair, there was no meaningful potential between any of them. I only checked STEP0- and DIR0- relative to GND and no meaningful change when jogging. I guess that means both are shot.

Replacing those two chips should not be too hard. I don't like that I don't know what caused the failure, I guess maybe some chip shorted it, since I have not messed with the electrical system in a while. I don't know how that would damage both chips, though.

Also, what are the overheating signs on U7? Is it that blob covering the 5?

Yes, a bump in the center of a plastic chip usually means its been overheated/damaged.

 You might check that the 27 Ohm resistor networks (RN1,RN2,RN8,RN14)
are OK as well (all 4 resistors per network  = 27 ohm)
A short to a bad voltage can damage these as well.

Checked all 16, all of them still read 27 ohm

Thank you both, I replaced U5 and U7 and my machine is working again.