Admin edit or create a page without parent page choice?

I make two plugins in my website . But I found there is no parent page choice in the edit page screen and create new page screen . I don’t know anything wrong happened .
The page attributes just has template selection and sort .No parent choice .

the chrome console shows:

api-fetch.min.js?ver=3.1.2:1 Uncaught (in promise) SyntaxError: Unexpected token < in JSON at position 0

and this line code is :

return t.json?t.json():Promise()

I thought it would be something wrong in the variable t , but I could not find it .
Help !&& Thanks for all .

• This topic was modified 6 years, 6 months ago by tomrui.