I have the same issue, I'm not able to open a CSV file in Excel. I've found a solution that worked for me in this question Opening a file in excel via Workbooks.OpenText
That question helped me to figure out a code that works for me. The code looks more or less like this:
Private Sub OpenCSVFile(filename as String)
Dim datasourceFilename As String
Dim currentPath As String
datasourceFilename = "\" & filename & ".csv"
currentPath = ActiveWorkbook.Path
Workbooks.OpenText Filename:=currentPath & datasourceFilename, _
Origin:=xlWindows, _
StartRow:=1, _
DataType:=xlDelimited, _
TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, _
Tab:=False, _
Semicolon:=False, _
Comma:=True, _
Space:=False, _
Other:=False, _
FieldInfo:=Array(Array(1, 1), Array(2, 1)), _
DecimalSeparator:=".", _
ThousandsSeparator:=",", _
TrailingMinusNumbers:=True
End Sub
At least, it helped me to know about lots of parameters I can use with Workbooks.OpenText
method.