Good morning, @Chandramani123456. 

It's great to see you back in the Community. Let me point you in the right direction to get this taken care of. 

Since you've already tired some troubleshooting steps, I suggest contacting our Customer Support Team so they can look over your file that you're uploading. Here's how: 

1. Go to the Help (?) icon in the top right-hand corner. 
2. Press the Contact Us button. 
3. Give a brief description of the issue and hit Let's talk. 
4. Scroll down and choose to Get a callback. 

It's that easy! 

Keep me updated on how it goes. I want to make sure that you get this file uploading in your QuickBooks Online account. Have a great day! 

@Chandramani123456 

Another option, utilize the trial version of csv2qbo converter to isolate the issue.

https://www.moneythumb.com/?ref=110

I'm having the same exact issue with a file format that I've used hundreds of times in the past.