Try aborting the build and redeploy.

this is a known issue with Metal builds specifically, still in Beta, several other threads report the exact same thing: stuck at "scheduling build on Metal builder", never reaching Cloning repo / Building image. Not something on your end, examples:

https://station.railway.com/questions/metal-build-environment-stuck-at-schedu-de9df979

https://station.railway.com/questions/builder-stuck-on-scheduling-build-on-me-c4bd27f3

https://station.railway.com/questions/scheduling-build-on-metal-builder-is-han-eeb28a0e

the mod's abort+redeploy sometimes clears it but isn't reliable per those threads. the workaround that's worked most consistently for others is turning Metal builds off for the service (Settings) and letting it build on the legacy builder instead, that unblocks the deploy while they sort the underlying Metal issue. worth trying that if abort/redeploy doesn't stick.