As you discovered with your other testing, the port is 443…
Blynk has a number of servers around the world, and your account/project only lives on one of them. In your case that’s the New York server.
Using the blynk.cloud url obviously leaves you at the mercies of the DNS service that you happen to be using at the time, but Blynk instituted some clever processing to automatically re-route your connection to the correct server. However, this doesn’t work with HTTP(S) API calls, so you need to specify the correct server when making these calls.
Personally, I’d stick with ny3.blynk.cloud url as it’s not beyond the realms of possibility that the IP address may change in future.
Pete.