Mechanical Keyboards

Is it hotswap or are the switches soldered into the board? If the former then yes, first thing to try is re-seat the switch in the socket, check that a pin on the switch isn't bent (and thus not inserting into the socket at all). The second thing to check (or first if soldered) is, using a multimeter, check continuity between the switch and its row/column and between the switch and its diode and check that it is working.

In either case, if re-seating isn't enough, corrosion or oxidation could cause the behaviour. If hotswap, check for corrosion or oxidation on the switch contacts and the hotswap socket. gently try to remove any layer of oxidised material with something lightly abrasive like sand paper, or even just insert and remove it a few times to try to rub it off. Clean with isopropyl alcohol. If still not working try to reflow the solder joints.

If all that fails you may need to run a small wire to fix a broken or corroded connection but that's unlikely I'd imagine.

Take it apart and see if the socket is loose. If it is get a soldering iron and fix it. Very easy many YouTube videos about it

It depends on which Royal Kludge keyboard you have. They make some that are typical mechanical boards (usually a cheaper Cherry MX based switch) and some that are EC Topre clones. If its the former, then you would probably need to take it apart and desolder the switches since I don't believe they made any that were hotswappable. If its the latter type, then you can pretty easily fully disassemble it and see if maybe something is up with the stems or conic springs under the membrane. Note: for the EC type, be careful when taking it apart and there is a good chance those springs will explode out like confetti and ruin your day. I learned this the hard way.