I have tried ... but I don't see any response from the ISS...
It's temporarily on 437.550 You also have to use a path like: ARISS,SGATE,WIDE2-2
That path adds 14 extra bytes to a packet almost doubling the length and therefore cutting throughput in half by doubling congestion. The only path necessary is simply VIA ARISS.
In most countries there are numerous IGates listening to the downlink and making sure the packets get to www.ariss.net and APRS.FI without the added path baggage.
Some have suggested adding the SGATE,WIDE2-2 on the end to force these packets from the SPACE frequency 145.825 over to the national APRS channel, but there they just collide with terrestrial traffic. I personally don't see the benefit considering the 50% overhead cost on the very precious 145.825 space freq.
Bob, WB4APR