These codes and banner text appear when there is an internet/connectivity issue:

EEC:IT invalid token – The token the device is submitting is invalid/expired/bad
EEC:MP missing params – The device is sending a request with missing required
EEC:SE server error – Our systems responded with non-OK / bad Server – Server might be unreachable or broken

Normal operation codes:

EEC:LR – This device is over your limit of subscribed devices. Purchase more display credits or remove some other displays. The usage is recorded once every 24 hours. Please allow 24 hours for changes to be reflected.
EEC:NS – this device does not have a subscription; you may also be seeing advertisements in the condition