The "No Line" message means that the base of the cordless phone either doesn't have power, the line is damaged or that the handset/base are not communicating properly. To diagnose the problem, first check that the base AC cord is connected to a good outlet. You may want to unplug the cord from both the phone and the wall outlet and then plug it in again. (I've seen a case where someone turned off a surge protector and forgot to turn it back on; without power, the cordless phone won't work.)
To check if the problem is the phone line, I like to use an old corded telephone. Plug the backup phone in and check for a dial tone. If there is no dial tone, try a new RJ-11 cord. If there is still no dial tone, try the test phone at another jack. If you can, find the box where your telephone line service comes in. Open the box and look to see if there is an RJ-11 jack. If that jack is present, try using the test phone and listen for the dial tone. If there is no dial tone at the service box, contact your phone company. They should fix this problem for free. (It's possible that rodents have damaged the phone line outside of your home.) If the box doesn't have an RJ-11 jack, you'll need the phone company to test the service and repair it if needed.
If there is a dial tone at the service jack, then you have an inside problem. If there was no dial tone at only the first jack, you can check the jack itself. Unscrew the face plate and look at the back of the unit. There are two types of connections. If you have the screw terminals, look for a disconnected wire. Strip a new section of wire and secure it under the correct screw on the face plate. See http://cablesupply.com/content/47-telephone-connections-and-rj11
for the wiring pattern. If the jack uses a keystone, you'll need a punch-down tool that is available in many hardware stores in the electrical wiring section. Do not strip the conductor; just push it down into the correct slot of the keystone. If the problem is not at the jack, you'll need to check all of the wiring from the service box for damage. Your telephone company will do this for a fee.
If the test phone had a dial tone at all of the telephone jacks, then the problem is with the cordless handset and the base. One of the two units is not communicating correctly (transmit/receive). If your cordless phone is still under warranty, contact Motorola. If only one handset can be used with the base, replace the phone. If your cordless phone can pair multiple handsets with the base and only one handset is giving the "no line" message, replace the handset.
I hope this helps.