Problem with .csv upload

Problem with .csv upload

I successfully uploaded a .csv file with 547 leads just the other day, but found there were issues with the formatting of the company names and phone numbers.  To make it easier, I deleted all leads from Zoho CRM and made the necessary corrections in the file, and then tried to re-import the leads with the corrected .csv file.  When I did that, I kept getting an import result of 0 - nothing is being loaded into the CRM system at all. 

What have I done wrong here? I've used Zoho for quite some time, and have never experienced this before. I have checked my .csv file thoroughly and don't see any reason for this to happen. The system is telling me the 0 result is due to a blank field in a required field area - but I have checked the .csv file, and there are no blank fields.  

I need to get an answer right away, please...time is critical on this.