Cannot add to project

Hi.
Have 3 EW300-PRO's.  Originally connected to ISP router providing a LAN connection.  Removed ISP router and entered PPPOE connection settings.  Now one of the units cannot be added to project.  I have connected directly to it and set to AP mode, connected it via lan to its WAN port.  I CANNOT, no matter what I do, add this unit into the project.  I have deleted projects to release devices.  If I login directly to 2nd unit, after setting to AP, it says AP mode is not correct even though it is working.  When I try to resolve this, the main router and this unit then resets to factory defaults and I have to start over again!!! This is INCREDIBLY frustrating and I have had to leave it this way with the main unit only showing on the project and the second unit connected which cannot not be managed by the portal.  WTF do I do to resolve this?

Hello sir,
Have a nice day!
You can refer to this configuration document: https://reyee.ruijie.com/en-global/resources/preview/reyee-mesh-routers-web-based-configuration-guide/