Not so fast. If the response of the Limit switches is slow, then Mach3 may have coasted a bit too far before stopping, and left one of the Limit switches still asserted, despite any attempts at backing off. That is probably the most common reason why the Reset button does not work (imh0).
At the risk of being risky (ahem), you could try putting a momentary press button switch in parallel with your Limit switches (assuming they are all NC switches). Pressing it will then allow you to Reset and move off the Limit switch.
Note: a momentary press button switch, NOT a toggle switch! You do not want any chance of the Limits being permanently bypassed. You could test the idea with a simple jumper wire with croc clips.
Cheers
Roger