The best way to get the router to list the devices under the Dynamic Clients lists is to turn EVERYTHING off accept for one wired PC.
Do a full on reboot of the router and let it come to ready.
Log in and go to Networking.
The one PC should be listed under the Dynamic Clients list. I recommend you reserve it. Select Reserve word link to the right in that row. It should auto fill in the Add Reserved IP address section above. Give it a name. Can be anything.
Select add then Select Save. Wait for the page to come back and continue.
Turn on the next device that you want to reserve. What for it to come to ready.
Refresh the routers web page or go to a different section then come back to Networking.
The new device should be listed under Dynamic Clients. Reserve it as you did for the first PC.
Do this process for each device that you want to reserve.
What Hardware version is your router? Look at sticker under router.
What Firmware version is currently loaded? Found on routers web page under status.
I would recommend doing this for all devices and let the router reserve and handle the IP addressing as thats what it's designed to do. This will help each device maintain it's own IP addressing with out any conflicts regardless if they are on line at the same time or not.
if you need more help, Maybe someone can review your router settings with you using
teamviewer.