cannot change this setting

[Willheee]

Can anyone explain what this is about? 

"Per new security guidelines, you cannot change this setting. Please contact your account admin for more information"

i am the only admin the only account holder 

[hafero]

same me to. because I must to change this setting for participant not login can be join

[MiloAnderson]

I'm having the same problem. I'm the owner of the account; there are no other users. Is this restriction supposed to be for my benefit? Who thought this was a good idea?