Hello Johanne,
Thanks for posting to the forum. The TA 6XX User Manual has a step by step guide for Voice Applications - https://supportforums.adtran.com/docs/DOC-3358
The ATM applications start on page 169 of the guide.
A red data LED indicates the T1 is down. Make sure your T1 cabling is correct. This LED will be green when the T1 is up.
Regards,
Geo