Battery

[Msroof]

My One is not holding its charge and also takes forever to upload to my phone.  Kinda frustrating when I charged it yesterday and it says it's low tonight

[WendyB]

How old is it?

That could be one of the reasons they do not last forever

but try these steps

Please clean the contacts
http://help.fitbit.com/articles/en_US/Help_article/My-tracker-s-battery-isn-t-charging/?q=not+chargi...

Then Do a Restart
http://help.fitbit.com/articles/en_US/Help_article/1186/?q=restart&l=en_US&fs=Search&pn=1

Also See this thread for charging best practices. If you are not charging it correctly you could be damaging the battery
https://community.fitbit.com/t5/Charge/Fitbit-charge-battery-problems/m-p/1323307#M53291

http://help.fitbit.com/articles/en_US/Help_article/1799

If that does not help contact support
http://help.fitbit.com/?cu=1