Sense setup taking hours

[ColonialMustard]

My Sense was connected and syncing, but any time I tried to do anything with Fitbit wallet (add card, remove, adjust any settings) the whole app would crash.

This forum suggested I just factory reset the Sense and delete/reinstall the app and do a fresh setup. So that's what I tried.

The setup is taking literal hours. The Fitbit app takes two minutes to connect to the Sense, and after entering the code, the app says it has to set up the Sense's firmware. After forty five minutes, the app said it only downloaded 18%. This is on strong wifi, able to support streaming movies, with no connection issues. It still is on "downloading" without switching to any installation or anything after two hours. 

When I set this up originally (same phone, still a compatible device according to the compatible devices list, same Sense) the whole process took under five minutes. What's going on? Why is this happening? 

How can I get this set up without having to spend literal hours while the progress bar crawls along?

[Odyssey13]

here are the support contacts I've gleaned over the years on the forums.

when there is someone available, chat is an option. Phone or Twitter works well, too.

https://myhelp.fitbit.com/s/support?language=en_US 

Support is limited by the number of representatives available at a given time and the hours of operation. Chat lines are open when they have live help.
USA: call (877) 623-4997
UK: call 0800 069 8505
INDIA: call 000 800 050 1057
IRELAND: call 01 691 7502 (country prefix: +353)
Other contact options:

USA: click

Canada: click for options