Uncaught (in promise) SyntaxError: Unexpected token '

Hello,

When I try to use a date/calendar module in the booking application of Gridbox, I encounter the following error:

Uncaught (in promise) SyntaxError: Unexpected token '', "div class"... is not valid JSON
at JSON.parse ()
at calendar.js:111:37
see image1.jpg

And I have a second question: how did you manage to combine text with the date-time selection and button, please?
see image2.jpg

Best regards.