Photos not eligible for competition

Earlier, I had no problems with this and could always enter new photos in the weekly competition, but recently when I have uploaded a new photo the site gives me the message that it's not eligible for any competitions.

I can't understand why it's not eligible for the next weekly competition. It's a new photo which I have not previously uploaded. Is there no weekly competition going on? Am I only allowed to enter on certain days?

Otherwise, could it be because they have the same name as other images I have uploaded previously i.e. "6" as I just number all my edited photos form 1 - 10 in a folder for each shoot so there may be duplication of numbers from different shoots but they're totally different images. 

I rarely upload a photo here and would like to be able to enter it in a weekly competition when I do.

Any ideas why this keeps happening?

Thanks.

Ruth