Canon EOS 90D DSLR Camera with 18-135mm Lens - Manual (Page 606)

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Troubleshooting Guide
Cannot reconnect to a smartphone.

Even with a combination of the same camera and smartphone, if you
have changed the settings or selected a diff erent setting, reconnection
may not be established even after selecting the same SSID. In this case,
delete the camera connection settings from the Wi-Fi settings on the
smartphone and set up a connection again.

A connection may not be established if Camera Connect is running when
you reconfi gure connection settings. In this case, quit Camera Connect
for a moment and then restart it.