Hi @alexfreitas,
The plugins that have that error message are are all made by the same author, BejoIjo. His plugins run a version check upon startup, in which they need to communicate with a server. In short, your plugin sends a version number and the server sends one back. If these numbers are different, then it will prompt you to update the plugins.
Of course, this all requires an internet connection. If you don't have an internet connection, you can't send and receive data from the server - therefore, it will fail to verify the plugin version. Put simply: you need an internet connection to use those plugins.
I hope this clarifies your concerns.
Zen