Quality issues rejection

If I'm correct, the flags are 3D renders, too.

You should get a perfect sphere.

Computers should be powerful enough to render this more accurately.

The same here:

And the eyelet should be set a little more precisely.

The texture for the flag is not seamless.

If you render things like this, consider adding the alpha channel and offering the asset as a PNG. That greatly expands the possible market.

The second flag is not very sharp.

For both flags, the background is grey, not white.

As for the backgrounds, you have colour clipping.

The Reviewers assess assets based on several criteria:

• Legal standards: Ensuring the content is free from copyright infringement and other legal issues.
• Technical qualities: Checking for image resolution, file size, and other technical aspects.
• Title and keyword accuracy: Verifying that the title and keywords accurately describe the image.
• Commercial value: Assessing whether the image is likely to be in demand by Adobe Stock customers.
• Aesthetic properties: Evaluating the overall look and feel of the image.
• Uniqueness: Determining if the image is original and doesn't duplicate content already in the Adobe Stock collection.

Compare your work with current Stock inventory. 

In what ways are your images better than what Stock has now?

As a customer, would you buy them?

• https://stock.adobe.com/search?k=saudi+arabia+flag
• https://stock.adobe.com/search?k=plain+background
• https://stock.adobe.com/search?k=plain+wallpaper

For starters, you should never upload the same image, one in color and one in b&w. The color version is enough. The buyer can turn an asset into black and white if they prefer. As for the asset itself, it's something anyone with a graphics program could create on their own with minimal effort. And the majority of buyers here are graphic design professionals. Why pay for something that they can easily make themselves?