Dial tones not received - 10ii

I just got a call-back (from Singapore) that I’ve been waiting for. It was a “press one if you’re …” system.

Despite me pressing multiple times and multiple options, the caller system did not receive the tone. I was able to hear the tones.

I tried calling my airline which has a similar system, and the tones I pressed functioned normally.

Strange … has anyone else experienced this?

For me there has been no problems with receiving the dial tones but - off topic perhaps but might be related- when starting a phone call there are no calling sounds: just silence which ends if the call is picked up.