Hi Chinthya,
Thanks for the detailed screenshots. However, we are not allow to use Teams for remote access support in our forum. We can only troubleshoot here in the forum. Regarding this point, we would truly appreciate your kind understanding.
A room mailbox is a resource mailbox that's assigned to a physical location, such as a conference room, an auditorium, or a training room. If you have a conference room that everyone needs to use, then you can create a room mailbox in Microsoft 365 for
each resource. See
Create and manage room mailboxes
As per the screenshot, I have notice that you have Default Duration set for Days 1.
Therefore, I would suggest you please change Default Duration to Hours and Minutes based such as screenshot below to check this issue.
If you still having problem then please provide us with the detailed screenshot about “the form is unable to accept the booking for more than 1 people” via the private message for further analysis.
Best regards,
Shyamal