Error when previewing completed form

Dear Sir/Madam,
I am creating a questionnaire in Kobo toolbox. It is my first time to use the software. The error below appears when I want to preview the questionnaire I created. I will be grateful for your support.
image

Sincerely

Welcome to the community, @mawa! Maybe you will need to validate your XLSForm through this online validator to see if there are any syntax issues.