Hello Vishal,
For the error : Tax classification for product XX missing.
Please check Business configuration activity : Tax Classification for Free-Text Items
Here you need maintain the appropriate settings.
For the error : Account Determination group is missing for product category
Check the Business configuration activity : Default Account Determination Group for Product Categories
Maintain the product category and its account determination group if it is not maintained yet.
This should resolve both the error messages.
Regards,
Harshal