Need some help here!

Good morning, or good afternoon, good night.

I'm having a strange problem, which is already pissing me off. I'm trying to upload an image as a cover for another fanfic I'll write in the future, but after forty attempts with different images, the message ''The book cover is inappropriate. Please upload a new one'' appears every time and Inkstone doesn't upload it, and this happened even with covers of the fanfics I'm serializing.

Obviously the images have all the requirements that Inkstone asks to upload an image, but the error persists.

I would like to know if you guys are having the same problem, or am I just the unlucky one.

The next chapter won't take long to come out btw.