It may well be that your original switch was fucked...and they do not 'screw' in...they have a threaded area on the end, to fit it; push brake pedal in towards the firewall [as if braking] the cruise switch is then inserted, as far as it will go [you'll hear a noise as the 'threads' pass through the brake pedal bracket]. Then pull the brake pedal back to its' normal position [this will probably push the cruise control switch away from the firewall slightly] and then the switch is 'set' at the proper level. The wiring harness goes onto the terminal farthest from the firewall. The manual says to do this twice; to be certain...I only did it the once because it is so hard to get to...
The original fault may have been caused by the switch not being adjusted correctly...the switch is designed to open circuit the power source to the module so that when you touch the brake pedal, cruise is turned off. If you put the wiring harness on the wrong terminal, cruise control will not activate or engage...
And a tip for anyone fitting cruise and having issues [just went thru this myself last month - **** it's good to have cruise control again...] if you make up a mini-jumper lead with 100 mm of cable and 2 crimp plugs on it; then insert into the 2 plug terminals so it acts as a 'jumper' then take the car for a drive; if cruise engages it is either a faulty switch or it is not adjusted correctly; if that doesn't work, the fault is elsewhere...
And if you want a real cheapie fix; don't even bother with crimp plugs, just bare 6 mm of conductor each end, twist the strands nice and tight, and force them into the looms' terminals for your temporary test...away you go!