The letters WC in this message stand for 'WebConnect.' WebConnect is the communication method that connects your inverter to the internet. Most inverters have a 'WebConnect communication module' that sends performance data externally.

The data transmitted by the inverter is sent to an SMA server in Germany. It is then processed into graphs and tables, which you can view via the SMA Energy app, the SMA Sunny Portal, or the Mijn Zonnefabriek app.

Sometimes, an issue arises on SMA's server side, preventing it from temporarily receiving incoming data. Sunny Portal then displays a message indicating a 'WebConnect error' because the 'device' is unable to 'log in to the server.' This is what 'WC Error: App Login to Server Failed' means.

This message is always temporary. The issue with the SMA server resolves itself, and the data will be received automatically afterward. Therefore, no action is required for this message.