Sense 2 stuck on a red X

[StellaAdams]

My just under 2 year old Sense 2 has not been holding charge, not syncing and switching off for the last couple of weeks whist I’ve been away on holiday.
I’ve now returned and done the full factory reset etc but to no avail. I still have the flashing Fitbit logo which then goes into the large red X. 
Please advise me on swift action before my 2 year guarantee runs out. Thanking you in anticipation.

Moderator Edit: Clarified subject

[MarreFitbit]

Hi there, @StellaAdams. Welcome to the Fitbit Community Forums. Thanks for bringing this to my attention and for the troubleshooting steps you've tried. I'm sorry to hear that your Sense 2 is stuck on a red circle with a white X. I understand your concern, 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:

• In the Fitbit app, from the Today tab, tap the devices icon and then tap on "Sense 2" and then "Sync Now".
• An update banner should appear.
• If the banner doesn't appear, tap on the devices icon and again on "Sense 2" then "Gallery".
• The app should show a pop up.
• Afterwards, try to restart your Sense 2: press and hold the button for 10 seconds until the Fitbit logo appears on the screen, and then release the button.
• If the battery keeps draining, please follow the instructions from this help article: Extend your Fitbit device's battery life 

[StellaAdams]

Hi there, thank you for your advice which I have followed but it has made no difference to my Sense 2. The battery didn’t last 24 hours and it still goes blank, then flashes the Fitbit logo then it just shows the Red X.

This is very disappointing as my Fitbit is not even 2 years old. Please advise on how to resolve this continued problem. 

[MarreFitbit]

@StellaAdams Thanks for getting back to me and for trying the steps I recommended. 

Since all the steps you tried didn't work, you have a Sense 2 and report it's not tracking your heart rate not sleep data, I need additional information from you that would best be shared privately. I’m sharing a link to a form for you to fill out so we can look into this further. 

This form is only meant for you to use, so let me know once you’re done. Click here to get access to it. 

[StellaAdams]

I replied to your link few hours ago, I hope this will resolve my faulty Sense 2 Fitbit, thanking you in anticipation: