I think that’s the problem. You are using an excel file in your Google drive. That is not a google sheet. You should create a new Google sheet instead.
After you create your new sheet ( you can type sheets.new in your browser to create a new sheet ) you can go to the File Tab>Import and Select that Excel file from the Dive or you can upload the Excel file that stored in your computer. Then you can name your sheet. And you will see it on Glide when you come to the select files section.
As has already been pointed out, what you have there is an Excel file, not a Google Sheet.
You can easily convert that to a Google Sheet by choosing File -> Save as Google Sheets from the menu bar.