Management Studio not working problem evaluation in standard version

Hi

We installed SQL Server Standard 2014 last 8 month and works perfect, but today when I try to start the management studio appears a message that evaluation period is finished and cann't open it. Our version is standard and I've never installed express version.

I try this

https://support.microsoft.com/en-us/kb/971268

but no solution.

What's happening? How can I fix it?

Thanks

santiago