Solved

Inactive host League info

The league host rules were adjusted and now you have to race in the league you want to be the host of. That message shouldn't matter with the beginners though, that's a general problem, it's more the Pro and Elite players looking for a new league that might be put off by it. The real problem is more that it means a manager racing in your league could take over host from you at any time.

Edit: Thanks Kevin for the link and quote, was you about going looking for that info.
Edit2: Yes, got to get ready for work now indeed.

Hi Seb
This is not a bug, it is intentional and was introduced a couple of months ago by the developers. See here New: Takeover from inactive hosts

The post is about half way down the first page, Jack said:
I have also just applied an update to this feature. If a host has not been in the league they are hosting for 14 days or more, they will also be classed as inactive.
So, if you are in a league where the host has been outside of your league for 14+ days, you can now take over hosting of that league.

At the time is caused much debate but the end result is what you are experiencing. I will set this bug report as "Solved".

Thanks
Kev.

Edit: Frank, you and I must get ready for work at about the same time LOL.