Dear Samsung Member,
Greetings from Samsung Customer Support!
Thank you for sharing your concern. We acknowledge your query and the battery-saving feature disables all network connections to save battery and issue might be happening because of it so please disable the power-saving mode then the issue also might be resolved.
In case the issue still occurs. Please register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Ask questions).
Thank you for writing to Samsung.
Samsung Customer Support