'Parameter is insufficient'

Hello,
Thank you for trying my plug-in.

I do not see the option ‘open’ but just a ‘-‘.

First , the “Teacher” user must edit their schedule .
“Scheduler” page:
https://olbsys.com/en/setup/special-pages/#edit_schedule

His schedule is displayed as “Open” on the following pages .
1) “Daily schedule” page:
https://olbsys.com/en/setup/teachers/#daily_schedule

2) “Weekly schedule” on the post “Teacher information”:
https://olbsys.com/en/setup/teachers/#teacher_profile_page

“Reservation” page is accessed with the URL parameter from links (“Open”) in these pages .

when I go to the ‘reservation’ page as a logged in member, I get the error saying ‘Parameter is insuffcient’.

“Reservation” page should not be accessed directly.
Because parameter will be insufficient.