It's worth testing your repair before you go to the effort of re-assembling your keyboard.

Lay the membrane back down in place, making sure it's the right way around, and feed the ribbon cable back through the slot into the logic board compartment.

Follow the instructions in Step 3, 2 and 1 in reverse and re-install the logic board and batteries. You don't need to put the grey plastic cover back on.

Connect the keyboard to a Mac computer and from the underside, gently press on each pad to check the corresponding key works.

If you find any key that is still not working, you'll have to get back in with the multimeter and find the fault. Remember it could be on either side of the membrane and it may not be visible by eye,