Sorry to hear you give up so easy. Steward gave you so wrong info. Should have caught that. Try just (xxxxxxxxxxx.)
Dial a # at the end of the dial string just to speed things up.
It’s just a matter of getting the dial strings to match what you want to send.
What did you dial in the Handy Tone when it worked?
Lastly I did not call the Linksys turds, I reserve that distinction for Granstream products.