Saving urls using the Pocket Pocket service service has failed within Firefox.
I am running the Windows 7 version of firefox with a couple of useful extensions.
The Pocket account has already been set up and authentication to the Pocket service works fine.
To make it work again, all the addons and extensions have been disabled for troubleshooting. No success.
I had to reinstall Firefox and delete my profile as indicated below :
How to successfully uninstall Firefox under Windows 7
Once completed and after adding the Pocket button into the firefox toobar, Saving urls with the Pocket service works fine again.
More information here :
Saving to Pocket and Accessing your List in Firefox