Charge 5 won't sync or pair with my phone

[JM29]

Yet another problem. Phone is syncing, but won't actually pair with Charge 5 now. What is going on?

Moderator Edit: Clarified subject

[MarreFitbit]

Hi there, @JM29. It's nice to see you around the Fitbit Community Forums. I'm sorry to hear that your Charge 5 is not pairing with your phone. I will do my best to help you with this! 

If you haven't done so yet, I'd recommend trying the following steps in the order listed:

• Unpair your Fitbit device from your phone's Bluetooth and Fitbit app.
• Unpair other Bluetooth devices that you may also have paired to your phone's Bluetooth settings.
• Force quit the Fitbit app.
• Turn off other Bluetooth connections when not in use. This can help to prevent connectivity issues or Bluetooth interference.
• Shut off your phone and turn it on after 1-2 minutes.
• Turn on the Bluetooth on your phone.
• Plug it into the charging cable and open the Fitbit app.
• Set up your Fitbit device.
• If there is no connection, restart your Fitbit device.
• Once your Fitbit device is paired and syncing, please proceed to set up your other Bluetooth devices to your phone again. 

With the steps above, what I want you to do is to pair your Charge 5 first to your phone's Bluetooth settings before any other Bluetooth device is connected to your phone. 

[JM29]

Done all this. Lost Fitbit /phone connection so I crossed my fingers and did a factory reset, losing last night's sleep data, but nothing incredibly vital.  This has
reconnected my phone to my Charge 5, and phone is syncing. However,  ECG app is still not working even though in Today - Health Assessments - ECG says is on and ready to use.
Cannot uninstall app in order to reinstall either.
As the ECG function is important to me, what do I do now?