I got this to work. I had to update the flycast app .toml
to the following
[http_service]
internal_port = 3000
auto_start_machines = true
auto_stop_machines = true
min_machines_running = 0
processes = ["app"]
[[services]]
internal_port = 3000
protocol = "tcp"
[[services.ports]]
port = 3000
handlers = ["http"]