While uploading csv file its showing error and not allowing me to upload csv file

Hi there, 27-00191275.

Can you tell me more about the error you are getting when you upload data through CSV file? This way, I can share with you the correct resolution of the concern.

However, we can start refreshing your browser to import them within QuickBooks Online. Click the Reload icon or press F5 on your keyboard. It could be that the error is caused by a full cache on our browser.

Let's try to fix it out by following the recommendation below:

• Use a different browser like Google Chrome, Mozilla, Microsoft Edge, and Safari. Then, try to import them in your QBO account again. It's a way to verify if the error is caused by having too much data in our browser.
• If everything works fine, that would be the time that we can clear the cache to help QuickBooks run better on your computer. 
• The other option is to use the supported browser in QBO.

I would like to include a few articles about importing data in QuickBooks Online. We'll surely get additional information about this process, and one of these is learning how to troubleshoot some errors.
 

• Manually upload transactions.
• Fixing bank upload errors.
• Importing bank transactions using Excel CSV files.

Just let me know anytime what specific error it is.  I'll be around to help you further as soon as possible. Keep safe!

Change/rename the file extension to lowercase.

.CSV to .csv

It worked for me.