It started happening with me today.
Somehow hkg region appears to be in bad shape.
I posted my troubleshooting here: Failed to start remote builder heartbeat: Couldn't allocate volume, not enough compute capacity left in hkg - #2 by heliocola
Somehow my account (or builder app) is stuck with hkg and even an older app in another region is not deploying.
I’ve managed to install docker, fix a symlink issue, and use --local-only.
Hopefully this will return to normal soon.
:hug-to-fly.io-ops-team: in case they are in need!