For me, it is good. Maybe, they thought it is just too simple?
first of all you are using a free picture on the web and very basic design that on my point of view can be achieve by everyone with little photoshop skill within 20 min also the image you are using are labeled as commercial use but with
referal link then on your image it would be impossible to show referal link or look absurd for a buiseness to display referal link on their advertisment
Try to be little more creative and door will open in front of you.
ps: i found the image with the phone number in the window that is actually a real phone number and may require that buiseness authorisation for printed work you should check that before.
Or it could just be that the mods don’t like it?
Probably nothing really wrong with it technically speaking.
I have done complex flyers that are technically perfect get binned, (just as most here have) so sometimes it all comes down to other factors, (you have done another accepted flyer that is too similar, too many in the marketplace, the idea does not sell well, etc).
Never take a rejection personally, or it is best to learn from it and press on.
PS you can use rejected flyer elements in the next one, just as long as it can be considered as a new product.