Here's our guide to reset the Wi-Fi settings in the SL2 camera in case you have issues with connection.
1) Push the Menu button on the camera and select Wireless communication settings in the function settings.
2) Select Clear Settings.
3) Confirm with OK.
4) Select Wi-Fi settings and click on Wi-Fi.
5) Enable the Wi-Fi.
6) Select OK to register a nickname.
7) Do not edit the name. Push the Menu button to confirm.
8) Select OK to confirm.
9) Back to the Wi-Fi settings, select Password.
10) Select None.
You are now ready to dissociate your camera from the app and to connect again your camera to the app: First steps with the SL2 / EOS 200D Pro Kit - WiFi (iOS)