R studio can't find object

From your screenshot, You did not import correctly the file. The column names are currently V1, ... V10 and not the one you expect (Participant, ... Q5).
You need to import your file using the correct function with the option header from first line activated. You can use the import Dataset button in RStudio IDE to help you.
You can read from Excel file or from text file as needed.

Also, please follow the guideline in the future for your questions and provide a reprex. Thanks.