You may be receiving this message due to your browser being stored with too much data. When there's too much data stored within a browser, it starts to cause errors or even glitches to occur within different softwares. Clearing your file data should do the trick. Don't worry. I'm here to help get you back to business. Follow the instructions below on how to clear your browsing data within Google Chrome.
Go to the Three Vertical Dots (Menu) in the top right-hand corner of the browser.
Pick History and then History again.
Click on Clear Browsing Data.
In the "Time Range" drop-down box, select All Time.
Press Clear Data.
Afterward, log back into your account and try to import the CSV file again. Here's a link that can provide you with some additional information about import transactions.
If your issue persists, please let me know so that we can look further into the issue to get it resolved as soon as possible. Bye for now!