It's probably "intellectual property violation"? You designed an iPhone... The round button is enough to violate Apple's design rights.
Are all these outright rejections? If the rejected artwork is placed in "Reminder", then it means you will need to produce a property release to say that you are the designer (owner) and the artist. You can just fill out the electronic form in which case no witness is required. Otherwise means the moderator have reason to believe you have included in your design, trademark, or logo that makes your art identifiable by the owner of the mark(s).
the comment was (translated):
During the review, we found that copyrighted elements are included. Therefore we cannot include your work in our collection. Elements protected by copyright may be found in the picture or description, title and / or keywords.
I guess it is the button of the mobile …
I suggest you remove the button and resubmit.
I changed the button into a trapeze and made the corners of the screen more round … let's see.
It worked … they have been accepted.
Thank you for your help!