cat 277 no aux hydraulics

That's a rough one to walk back from since it went from "one button dead" to "nothing works" right after reassembly, which almost always means the teardown disturbed something internal rather than a coincidence.

Most likely, in order:

1. Internal connector or ribbon lead knocked loose during reassembly. Many Cat two-button joystick handles have an internal PCB with a small header connector or soldered leads to the switch/Hall board; these are easy to reseat wrong or crack resoldering by hand. Pull it apart again and specifically wiggle-test every internal connection with a meter while flexing gently.
2. Micro-switch or Hall-effect element misaligned on reassembly, no longer making contact when the button is pressed. Field reports on Cat CTL/skid steer joysticks show this exact failure pattern after the stick's been opened.
3. Wires reconnected on the wrong terminals at the base connector. If there's a detachable header inside, it's easy to rotate it 180 degrees or swap two similar-gauge wires.
4. Less likely now: aux ECM. You'd already isolated the original single-button fault to the joystick side by ohming the machine harness, so the ECM was probably fine before you opened the stick.

Concrete checks: with the joystick connector unplugged, back-probe pins at the connector for your reference voltage and ground (on these sticks you're typically looking for something like 8V supply, a ground, and a signal wire that should sit near mid-scale at rest and swing toward the rails when the button is pressed; if your signal wire is floating high with the joystick unplugged and won't move at all with it plugged back in, that confirms an open circuit inside the stick, not a wiring fault outside it). Compare readings pin by pin against what you measured before disassembly if you recorded them. If nothing moves on any pin no matter what you press, suspect the internal ribbon/connector over the individual switches, since a single dead switch wouldn't kill every function at once.

If the internal connection can't be found or reseated, you're looking at replacing the OEM joystick assembly (consult your parts manual for the exact part number by serial number range, since Cat's two-button handle went through at least one connector revision — the original 2-button joystick handle was a 159-5751 (6-pin connector) that updated to 218-6118 (12-pin connector), and to successfully marry the new Part Number of joystick handle to the old-style wiring harness on the machine requires a 242-8277 jumper harness. Getting the wrong revision without the jumper harness will look exactly like your current "nothing works" symptom). Aftermarket sticks off Amazon/eBay commonly show up with a different pin count than the original, so verify pinout before splicing.