Each time the plugin is deactivated, the license if removed ( so you can install it on another site).
If the plugin was deactivated without going through the deactivate menu on the plugins screen (such as renaming the directory or deleting the directory),
then plugin also can go out of sync.
If you have trouble saving the license key, please try the followings:
1: please check your license keys on NeahPlugins.com and delete any activation first.
2: deactivate and re-activate the plugin
2: Please make sure your server firewall is not blocking calling to neahplugins.com