The PNLC1017 is the charger for the handset of some Panasonic cordless phones. One of the compatible handsets is the KX-TGA660 which works with the KX-TG4112 system.
However, the 'Check tel line' message indicates a problem at the base or the POTS (Plain Old Telephone Service) telephone line. The system is not hearing the dial tone. Check that the power adapter is plugged in to a live outlet and is warm. If it's cold, than the power transformer is not working and the base has no power. If there is power, check if the handset message disappears when the handset is close to the base. This is usually rare but indicates a transmitter/receiver in the handset or base is not communicating properly. You can try to de-register all handsets and then register them again.
To check the phone line, I prefer to use an older corded phone. These don't require power to work. First, try a new phone data cord (RJ-11) between the base and the wall jack. (I've seen someone accidentally use a handset cord which doesn't work.) Test if there is a dial tone when this cord is plugged into the test phone. If there is a dial tone, then if the cordless phone base didn't work with the replacement cord, the base is faulty. Replace it or contact Panasonic if the system is under warranty. If you have a DSL fliter, this may be damaged. If it's inside, replace it. If it is in the service box, ask your telephone provider to check it.
If there is no dial tone, you need to locate the other phone jacks for that phone line. Find where your phone service comes in as well. Check if there is a dial tone on another jack for that phone line. If there is no dial tone, check the service box for an RJ-11 jack, Test for a dial tone there if you can plug in the RJ-11 cable. If you have a dial tone at another jack, then the problem is local to the first jack's wiring. You can open the jack and check for loose wires. There are two styles of jacks - screws or punch-down. For the screw terminal, strip the insulation and wrap it under the appropriate screw. For the punch-down keystone jack, you need a punch-down tool. The tool is available from most home improvement/building supply stores, in the wiring section. Do not strip the wire. Use the tool to press the wire down into the correct slot on the jack. See https://www.lanshack.com/wire_phone_jack.aspx
for the wiring diagram.
If you can't test the phone line or there is no dial tone at the service box, then you need to contact your telephone provider. It used to be that the provider would always test and fix outside problems for free. Some telephone companies are trying to stop repairing copper wiring. If you have a dial tone at the service box, then the problem is somewhere in the inside wiring. You may want to get someone to find a broken wire in the wall for you. Your telephone company service technicians will do this for a fee.
I hope this helps. I've had the check tel line issue times several times at my home. Twice, the outside line was damaged by mice and repaired by my telephone company. Once, a lightning strike damaged the DSL filter; it was promptly replaced. Other times, the line was damaged by contractors digging too close to the underground utilities. The contractors got the wiring repaired. When our service was switched to a fiber-optic system, we lost one telephone jack when the installer simply didn't plug in the wire. We found the loose wire behind the siding and plugged it into the port in the service box ourselves. Since then, we lost telephone and other service intermittently when the modem card in the service box was failing. That was also replaced by the telephone company technician.