A short guide on what to do when you see an error related to API.
First, make sure that in your exchange API settings you have enabled the fund query option and the trading option (the title may differ on different exchanges).
Second, please check that your API connection in WunderTrading settings is active. If it has an error please press the "edit" button and "edit" again, it will re-connect the API.
If the API is connected you will be able to see your balance in My exchange settings, in Dashboard and the Terminal.