Cany install WPMUDEV on http://irishlakelands.com

Hi, I have successfully installed WPMUDEV on several other of my sites. But when I attempt to log in after uploading and activating the plugin on http://irishlakelands.com I get the following error screen message.

code “rest_missing_callback_param”

message “Missing parameter(s): username, password, redirect_url”

data

status 400

params

0 “username”

1 “password”

2 “redirect_url”