As of September 2014, YouTube's own keyword tool stopped working. It was moved over to Display Planner's AdWords video keyword suggestions. To use it, you need to have an Google Ads account. Just like the non-existent YouTube keyword tool, it was created to facilitate paid video and ads promotion. Which is why keywords that you will find there might not be closely related to the topic that you want to cover.
I just tried and its working fine from my end. When clicking on the link, you should be taken to the SEMrush page where you should be able to grab SEMrush pro account for free for the next 14 days worth $47. Please clear cache for your browser and try then. Please let me know if you still face any issue in claiming the 14 days SEMrush pro account for free.