Here is the response I got from SMG regarding this.
"Thank you for reaching out!
We've just entered a new season in RISK, you can view how seasons impact ranking for all players in this support article: Ranking Updates [v3.8]
Our standard How is my RISK rank calculated? article explains in more detail how rank changes within seasons / each game.
For Grandmaster players - we're currently working on a fix for the rank points threshold being 21,000 instead of 26,000. We have a News post in-game that will be available shortly (if not already!) to clarify how this will impact current Grandmasters and how it will impact players that were Grandmasters and reverted to 21k instead of 26k.
Once our news post is live if you have any other questions surrounding the Season/Rank information let us know and we should be able to help clarify these for you!
All the best,
Luci@SMG"
Alasdair Alexander