App in general

Q2: Why can’t I pair the app with my phone? What should I do when the connection between the app and the watch is unstable?
A2: ・Restart your phone, tap the CASIO WATCHES app, and then follow the on-screen guidance to pair (or reconnect) with the watch.

Refer to the sections below in the User's Guide.

● First-time pairing: Pairing the Watch with Your Phone
Pairing the Watch with Your Phone

● Reconnecting: Connecting With a Phone Paired With the Watch
Connecting With a Phone Paired With the Watch

・The watch will not connect with a phone while it is in Airplane Mode. Turn off the watch’s Airplane Mode to connect.
Entering the watch Airplane mode

・In some cases, the problem can be resolved by first unpairing the watch from the phone app, watch, and smartphone OS, and then performing the pairing operation again.

・Data already captured by the app remains stored in the app even after unpairing.

Unpairing
Unpairing

・Also refer to the settings described at the URL below.

Why can't I establish a Bluetooth connection, and why does the phone app no longer work properly?
SmartPhone link
BD-H2000(3515)