Hi,

After you reset it, the username and password are both admin. Normally, you have two ways to manage the EAP. 

1. If you want to manage the EAP in standalone mode, you can input the IP address of the EAP or tplinkeap.net when you connect your client wirelessly, or you can input IP address when you connect your client to the EAP by a wired connection. 

2. You can also manage your EAP by Omada Controller; you say you can not adopt the EAP and the error message is "Failed to send Command." You can try to close the anti-virus/firewall first for checking. Or you can also use different browsers to have a try.