Hi,
I am getting above error while creating "New Flow"(flow builder) in my playground org or Dev org. 
There is a challange to be completed for Trailhead topic: Guide Users Through Your Business Processes with Flow Builder , where we need to create Flow. When I launch my org > navigate to Setup > Flow > and click on New flow then respective error is displayed. It also states "refreshing" page can help, but I refereshed the page several time ,still its not working.

Please help me onresolving the same , so i can complete my trailhead challenge too.

Thanks in advance.