Original art work got rejected for technical problems

My guess: Someone looked at it like a photograph.

It's hard to comment because I don't know if you submitted this as a vector graphic or a raster image. 

Most often original artwork is rejected for a) not complying with submission requirements (see below) or b) failing to include a signed property release.  Adobe doesn't know you're the artist until you tell them.

https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/property-release.ug.html

Please re-read the section on Content Requirements in your Stock Contributor User Guide.

• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/vector-requirements.ug.html

Hope that helps.

Hi @Anastasiia M. ,

I believe  it is because you have a few patches like this without distinct edges. 

Best wishes

JG