Some IVR doesn't recognize my asterisk DTFM

I have a problem that some IVR (call centers of other companies I call, for examp telecom or assurance) doesn’t recognize my actions when I’m in call. The voice tell me ‘press 1 to go to operator’ and when I press 1 nothings happen. Then I need to use classic analogous phone to make this call.

There are other call centers that recognize my actions.

What can be the problem and eventual solution?

I use asterisk 1.4.1 and Snom 300 phone.

Its DTMf issue. which mostly located within Asterisk & ur end points.
1st there is no mismatch between Asterisk DTMF option & your endpoints dtmf snom 300.
also try with diffrent dtmf type on Asterisk & check. chance of telecom carrer side issue is very less u can ask them what dtmf they support. Aslo in sip.cong u can set dtmfmode=auto for better result.