@Moulders 

Ensure your Tapo app is updated. You may try to delete and reinstall the app. Do not enable VPN (if any) on your phone while using the Tapo app.

Try to use another phone or tablet. 

If the issue persists, contact support team for further investigation. Contact Technical Support It will be better to submit an app log and include a screen recording of the problem. How to get the log of Tapo app