Why can't I make my tournament rated ?

Hello,
I created a tournament for my team, and it's somehow casual. So I try to make it rated by going to the setting, but when I click "save," it's not changing anything.

Could somebody help me fix this issue ?
The link to the tournament : lichess.org/tournament/kCoULFMl

Thank you very much.

Hi!

I see your Arena uses a custom positon.

I see in the API documentation for instance,
that custom positions can't be rated - ("position" parameter in lichess.org/api#tag/Arena-tournaments/operation/apiTournamentPost )

Edit, including the text here:
"Custom initial position (in FEN). Variant must be standard, fromPosition, or chess960 (if a valid 960 starting position), and the game cannot be rated."

Thank you for your response @tors42,

I must say that I find it a bit annoying that I can't make a rated tournament from a custom position, as there are rated arena tournaments with custom positions in the lobby. But lichess must surely have their reasons.

Oh,
it seems some thematic positions can be rated.

I just tried to create an Arena,
with default values,
and put the FEN of the "French Defense" into the "Starting position" field: rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2

And the Arena got rated.

If I use a "Starting position" where I move the King for instance: knbqrbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2

The Arena is casual.

So it seems to depend on which position you choose to start from...