EDIT: On the 9th of November around 13:30 UTC, we released a fix and you should now be able to enter for free the 1st Grand Prix in any Weekly event.
Additionally, we deployed compensation for all players that will add Tokens directly to your in-game currency wallet. This Tokens compensation is calculated based on the number of Grand Prix from Weekly Events you have already joined that were supposed to be free and weren't (due to this bug we have just resolved) when you joined them.
With the release of Update 30 on the 12th of October, all Weekly Events have their first Grand Prix free-to-join. Unfortunately, there were some technical issues and as a result, you would be debited Tokens for all the Weekly Event Grand Prix.
This is a known issue that we are currently investigating and we will update this article as soon as we have any news to share.