Rated 4 out of 5 stars

In Firefox :
- check that kwallet extension is well ACTIVATED
- connect to Firefox Sync
- unactivate Kwallet extension
- restart Firefox
- check that kwallet extension is well UNactivated
- connect to Firefox Sync
- go to Firefox password manager
- copy somewhere the password of "chrome://FirefoxAccounts (Firefox Accounts credentials)"
- activate kwallet extension
- close Firefox

In KWalletManager :
- search the entry "Firefox Accounts credentials"
- replace the password by the password you copied somewhere

In Firefox :
- start Firefox
- it works !

Explication : passwords(tokens) delivered with or without Kwallet extension are differents
A correct password looks like :
{"version":1,"accountData":{"kA":"e4...45","kB":"9c...9e"}}

This review is for a previous version of the add-on (1.1).  This user has a previous review of this add-on.