Lost communication with base unit. I'm following instructions in manual to re-register but it keeps comming up error

Some Panasonic cordless phones come with up to five handsets each will need to be properly adjusted. You may need to set the main handset to synchronize with the base unit plugged into the telephone wall jack and assign special configuration numbers to the other handsets in order to properly identify each one within a specified location. One handset left in the turned on mode may make it impossible to place calls with the any of the other handsets. This will continue until either the battery dies or fails on the handset or the phone is switched off and replaced in its charger for charging again. Synchronize the main handset by pressing the MENU button on the handset, then pressing the down button IN order to select the number you wish to assign to that handset. Repeating this process if you have already done so will greatly decrease the level of errors experienced with panasonic phones MORE USEFUL INFORMATION FOR ALL YOUR ELECTRONICS When troubleshooting these units, there are always several variables to consider. First check to see what last occurred with the unit such as did the children play video games, did the electricity go out due to bad weather. You may see that there are many possibilities but let's focus on what occurred last to the unit. Once we determine what happened last, we may isolate the actual cause of the problem. The actual cause may be associated with projection issues, older versions (Picture tube), interference from devices located nearby, and even a radio turned on and located really close to your unit. This is normally known as electromagnetic interference to electronics and is very common with the error you have provided today. Please continue to look for anything EXTERNAL to the unit before looking at the internal components. I have been working on these a long time so feel free to follow up with me.