Sharepoint list online isn´t showing the customize option to powerapps

Hello Everyone,

I have been a problem using the sharepoint list online, I don´t know what happened but the option of costumize my form with powerapps disappeared.

Because of it, I am not getting integrate the sharepoint with powerapps . 

Attach image: "error 1" lack the option custom by powerapps , "certo" other sharepoint list with the option and "error2" in form settings lack the option "custom by powerapps".