Error with Please submit a valid csv file. - Invalid byte sequence in UTF-8 in line 57.
This error may be due to an issue with the formatting or content of your CSV file. Try opening the file in Google Sheets and then downloading it as a CSV file again. This process can often resolve any hidden formatting issues. If the problem persists, consider checking the file for any special characters or non-UTF-8 compliant characters, especially on line 57 as indicated by the error message.