Why wasn't my job accepted?

[Nicoskin]

This job was accepted

This job was not accepted

I don't understand why I get a technical problem? One is accepted by the other with the changed color no. How does it work?
I attach the works that were not accepted.

 

[Abambo]

I won't look into all you pictures, but all pictures I've looked into have problems:

Please check your images for artefacts before submitting.