Using SharePoint Online Migration Manager unable to sign in to DropBpx

I want to migrate my DropBox folders to a SharePoint Online document library.

now i did the following steps:-

1. Go to the migration manager >> click on sign to dropbox >>

1. Sign in using google:-

1. but i will be redirected to the same page (API Request Authorization):-

1. and the Migration manager keep showing the following message:-

so any advice?

Thanks