@AbuSulaiman
Hi,
Usually, opening the Deco app won't affect the Deco nodes' performance. In your case, please provide the following information for further analysis.
1. Do you mean your Deco nodes are working fine(with a solid green light) and will be offline(with a flashing red light) once the Deco app opens? Does the main Deco have a flashing red light when the Deco app opens?
2. How many Deco nodes do you have? Please describe your network diagram in detail.
3. Do the Deco nodes work in AP or Router mode?
4. Please log in to the Deco's web UI > Advanced > System > Firmware Update, check the Deco nodes' firmware version, and send the version info to us.
5. Please ensure your Deco app is up to date.
Best Regards