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Power-cycle the terminal
Disconnect and reconnect the phone cable from the terminal and the phone/line port.
Make sure the phone cord is plugged into the correct port on the terminal. (Line Port)
Confirm phone line has a dial tone with no pauses or beeps beforehand.
Check if long distance works by calling our auth numbers (18002281257 & 18772664012) on their line.
Confirm they're not on the same line. If they are, call their cell phone or call them back after every step.
Confirm if terminal is on a or sharing the line with splitter another device/phone.
If so, try to remove it and connect directly to the phone jack.
The phone cable may have a short, try a different physical phone cable.
If they say they do not have another phone cord, ask them to use the cord from their telephone.
Try a different wall jack, if available.
Confirm if they are using an Analog or Digital Line.
Software Troubleshooting
Check that the correct comm type is set.
If you are getting connect errors, the terminal might not 'hear' the dial tone, try disabling dial tone check
Confirm if the merchant needs a dial prefix or pause
Check Terminal Comm settings:
Try changing the baud rate
Check that the appropriate auth numbers are set on the terminal
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