I have two R500 and each shows as Master under Access Points (i.e., two masters and no members). I have attempted the following without success to have a single Master and rest as members:
both R500s are on same network subnet and can ping each other
tried set both APs with static IP addresses or DHCP
tried factory reset by pushing reset button with paper clip for 10+ seconds and from rkscli "set factory" command
tried to force either AP as member from rkscli "set election role 1". This did not work. Able to ping and ssh but only shows "Building the Unleashed Network. It may take a few minutes." on browser infinitely.
tried both settings in System>System Info>Preferred Master to No Preference or selecting it as master
checked both AP country code are the same "United States"
Note, did not have this problem before. It worked for more than two years until recently. Not sure what caused it maybe a power outage. First time noticed problem after seeing "Disconnected 1" under Access Points. So clicked remove and rebooted. After rebooting, both becomes Master.