Welcome @Ynske
When a file cannot be transformed from txt to tabular, it usually indicates a formatting issue. This can be pretty common after some manual changes. And some of the text editing tool can add in odd characters too!
We have a tool that can screen through a file to convert any whitespace to a tab and remove any duplicate whitespace characters. You could give this a try to see what results. If nothing else, it would allow you to see where any problems are located. You could try this with the original file too if it is in plain text.
- Convert delimiters to TAB
We also have many Text Manipulation tools if you need to do more! These tutorials are a good introduction if this is new to you!
Please give this a try! If you get stuck, we can help more if you share your history with the file for some feedback here. 