Elk M1 Dialing Problem

I have an Elk M1 Gold that is experiencing a problem with the panel dialing central station.  It seems that the panel only dials out about half of the time.  I have verified that the dial tone is present, and the zones are configured properly.  As well, the same zone being triggered will dial out sometimes and not others. The zones always trigger the siren appropriately.
 
Can anyone recommend troubleshooting procedures, or a way to test the dialer?
 
Thank you!

It might help to see that rule that triggers the dial.

Mike

Sorry, it's basic if a zone is tripped while armed.  IE if the front door opens while armed in instant mode, it triggers the siren and should (and always did previously) dial the central station to report.  For the last few months, it triggers the siren and only dials out to report sporatically.

If I remember correctly, the only way to dial out is through a rule. Are you familiar with ElkRP2 software and rules programming?

mikefamig,
Thanks for the help.  Yes, I'm familiar with ElkRP.  I did the installation and programming about 7 years ago, and it has worked perfectly until about 3 months ago.  Here are a couple of screenshots that will hopefully help explain what my setup is.
Thanks again for any help figuring this out.
 

I was wrong when I said that you must program a rule to dial out. I looked at the installation manual and it is only voice type dialing that requires a rule to dial out. You might try adding one or two commas at the beginning of the phone number. It will cause a short pause before dialing. That will help ensure that there is a dial tone.

Keypad programming from page 38 installation manual
 
These are the digits to dial for the selected telephone number.  Up to 20 digits may be
programmed.  Valid number digits are: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.  In addition, special
characters may be entered such as comma (,) for 2 sec. pause, slash (/) for 125 msec
wait, # and * for touchtone signaling, plus the letters A, B, C, & D.  The cursor
automatically moves right each time you enter a number digit.  To enter a special
character place the cursor where you want the character and press the up arrow key.  The
1 key produces a 1, #, *, and /.  The 2 key produces a 2, A, B, and C.  The 3 key
produces a 3, and a D.  When finished with a special character you must press the down
arrow key to return to number digits.
 
Mike.

I just looked at my settings and I have two slashes at the beginning of the phone number and it has been working for me.
 
Mike.

Any recent changes to phone service, IE: POTS to "digital voice" or similar? Any changes to phone wiring?