"fail: Test ADSL Line Sync" per AT&T Tech Readout

hi,there are a lot of possibilities y ur dsl light wont stop flashing red, 1.could be hardware failure,2.defective lead light for dsl,3.or line issue on the network...i strongly recommend that you contact your isp or att provider so that test would be done by their tech support,...basically you have checkd all inside wirings n as you have said you even tested the nid already...have you tried changing the dsl cable or phone cable? have you tried using another modem? were you using a filter for your dsl? you have to consider also other emi/rfi or electronic interference....but most probably you might try upgrading your modem n see if your gonna get a steady dsl light...the ethernet plugs has no effect on the dsl light...its just the cable connection or line issue or defective modem...i hope this will help, pls feel free to ask if you need further astnce...