Vault has been working before but then I restarted the server and I get this:
WARNING Vault not loaded, please check your plugins folder or console. Vault is in my plugins folder and I can not find the problem.

check with the plugin that's telling you it's not loaded, or optionally post your server log.

Alright I see that Vault is working on some plugins but the one that really bothers me is that my ranks no longer appear from groupmanager do you know what I should do?

As I said, contact the plugin that you're having problems with.