it's the r key on pc

Happened to me too
I think a gmod update ruined it

I tried r and it still wont start. I don't know what button to push, I've tried to press every button but it wont work.

Same. No more options for key bindings

Yes i tried the same thing and it also wont start literally pressed every button on my keyboard and nothing happened.

Try pressing 1 than r. That worked for me

ok

No its easy just use r key

it still dosent work i pressed the r key but its not working AAAAAAAAAAA

doesn't work WAC
and LFS Too

for me it does't work sometimes, I will spam the R key but nothing happens, and then re-spawn the vehicle and it will work again

you have to sit on the sit where you drive. Just get in your vehicle, press 1 to be sure that you are on the driver's seat, and then press R

It is probably some weird mod conflict because sometimes I get a bug where I can't get out or start the vehicle. It happens with both WAC and LFS when it happens for me.
When I unsubscribe from certain mods it returns to normal

But to be honest I have no idea