WordPress SEO by Yoast problem

HI, there. I hope someone can help me. I had my SEO plug-in by Yoast working perfectly, a green light on all of my posts. I’ve changed nothing, but suddenly I have a red light on every post, when all the key words, meta etc are just as they were before when they were green lighted. I clicked the bad check to see what might have caused this sudden change, but everything is as it should be. Is there a new glitch in this plug-in that I should be aware of?

Thank you in advance.