Sleep stages on app occasionally not working?

[SunsetRunner]

Hey all hope you're all well. 

Sorry if this has already been questioned I'm not on great terms with technology lol. 

So I have had sleep stages for quite some time it's extremely insightful but for some reason it doesn't work every day. I just updated my tracker (charge 2) to my phone (android) and most days still show up in the old way the I'll get sleep stages for maybe two days then it goes back. It's been a few weeks now did I break something? My partner also has this problem but not nearly much as me and it seems to be on nights he doesn't wear his. I never take mine off at night. Sorry if it's a bit of a garbled question and thank you in advance for your comments/suggestions. 

[SteveH]

Fitbit suggest there are a few reasons this can happen:

"WHY DON'T I SEE SLEEP STAGES TODAY?

There are a few scenarios where you might see your sleep pattern (which shows your time asleep, restless, and awake) instead of sleep stages:

• If you slept in a position that prevented your tracker from getting a consistent heart-rate reading or wore it too loosely. For best results, wear your tracker higher on your wrist (about 2-3 finger widths above your wrist bone). The band should feel secure but not too tight.
• If you used the Begin Sleep Now option in the Fitbit app (instead of simply wearing your tracker to bed). For more information on automatic sleep tracking, see How do I track my sleep?
• If you slept for less than 3 hours.
• If your tracker’s battery is critically low."

taken from: https://help.fitbit.com/articles/en_US/Help_article/2163/

[SunsetRunner]

Thank you 😄