why this photo is not able to be uploaded from Lightroom classic

The Lightroom plug-in for Adobe stock does indeed all the hard work for you to upload the pictures to stock, except that LrC's keyword sorting is absolutely not ideal for stock. If it does not work out, however, you need to give us either an error message or something else that allows us to guide you.

I'm sorry, but my crystal ball is currently under maintenance, so I have no idea what happens to your uploads. (sorry for being sarcastic, but we are users, and we do not have access neither to your computer, nor to your account. We can only advise on the hard facts that get presented to us... 🙂 )

If you are new to stock, you should consider these resources: https://helpx.adobe.com/stock/contributor/tutorials.html
Please read the contributor user manual for more information on Adobe stock contributions: https://helpx.adobe.com/stock/contributor/user-guide.html
See here for rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
and especially quality and technical issues: https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

Read the Adobe Stock Contributor User Guide for details on image requirements.

Photo Dos and Don'ts:

https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/editing-dos-and-dont.ug.html

Tutorials:

Check out the Photoshop tutorials, Lightroom tutorials, and Lightroom Classic tutorials on everything from adjusting an image’s tone and color to sharpening.

Technical requirements

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

• Submit images in JPEG format.
• Use color space sRGB
• Minimum image resolution: 4 MP (megapixels)
• Maximum image resolution: 100 MP (megapixels)
• Maximum file size: 45 MB (megabytes)
• No watermarks or timestamps
• Do not upsample your files; submit the maximum file size that your camera can produce.

I'm not quiote sure what you are asking. When you publish to Adobe Stock, the application creates a temporary JPEG file which is uploaded to Adobe and then deleted on your computer.

If you want to create a JPEG file for yourself or for some other purpose, you need to use the Export function.