Please do not connect the M5 to your phone directly in the Bluetooth settings of your phone.
Connect the M5 via Bluetooth only through your Morpheus app by way of TEST, TRAIN, or SYNC.
The M5 band will not connect to the Morpheus app if it is already connected to your phone's Bluetooth settings or another device directly via Bluetooth. The Morpheus app likely will not even be able to see your M5 band as an option to connect to if your M5 is already connected to your phone or some other device directly via Bluetooth.
If you ever see a Bluetooth symbol on the digital clock interface of your M5 (such as the picture below) when you are not actively connected to the Morpheus app for a process such as TEST, TRAIN, or SYNC, it means your M5 is connected to your phone or something else directly via Bluetooth when it should not be, and this will cause connection problems with the Morpheus app.
There is both a temporary and permanent solution to this issue.
Hard reset the M5. This will temporarily break the Bluetooth connection and will allow you to connect to the M5 in the immediate term but is not a long term solution. The Bluetooth connection will just come back eventually.
The hard reset process is:
Hold the side button for about 10 seconds.
Let go of the side button.
Then sync the M5 to the app by pressing SYNC in the app.
This will break the Bluetooth connection and will temporarily allow you to connect to the Morpheus app - to complete the recovery test, for example.
If it is your phone that the M5 is connected to directly, you will need go into the Bluetooth settings of your phone to "forget device" or otherwise remove that connection.
If it is not your phone that is connected to your M5, then you will need to find whatever the M5 is connected to and remove that connection. And make sure that it does not get paired or connected directly to a phone or other device's Bluetooth settings again. The M5 will not automatically connect with any device because Bluetooth connections of this nature have to be confirmed by a person.