Error message when opening Trados Studio: Service 'Sdl.TranslationStudio.Api.ProjectManagement.IProjectManagementService' could not be started

I was working with the progrann the whole day and in the evening I could'nt open it. I got the messagge: 

Error message when opening Trados Studio: Service 'Sdl.TranslationStudio.Api.ProjectManagement.IProjectManagementService' could not be started.

I ' ve tried to solve the problem  by meself with the help of instructions on the site but nothing worked.