It would help to know, which Anki version and importer (legacy or not) you’re using, and to see the exact error message.
To debug yourself, you could remove parts of the CSV to narrow down the issue. You could also upload your deck somewhere so we could take a look.
If I had to guess at the issue, I’d say a likely culprit is that the file is not actually in UTF-8 format. If you can upload it somewhere so we can download it, we can check.