I've downloaded Box, Dropbox and they show up in the options.

What exactly does this mean? Please be more specific.

If you want to use Dropbox as a Filelink provider, you'll need to install this add-on. https://addons.mozilla.org/en-US/thunderbird/addon/dropbox-for-filelink

1) Add-on's were installed image #1. 2) Image #2 is of when I attempt to choose which Filelink service I want to use (< > which is what?). 3) Image #3 shows Filelink just scrolling/working to upload, to what service Dropbox or Box I don't know. 4) Upload runs for many hours and the file never gets uploaded to the service. 5) I have uninstalled Add-ons and re-installed them both and separately. 6) Months ago the feature worked and I was quite happy, was there an update that may have caused this problem if so can I re-install the previous version in order to get the feature to work for me again? I look forward to constructive options to resolve my problem, Thank you.

What happens when you remove one provider? Still seeing the problem?