The Weebly/Booxi integration does not support the booking widget v3.
Sign in to your Weebly account.
On the website editor page, scroll down to the "Installed apps" section and click "Add app"
Weebly's app center will open. In the search bar, enter "booxi".
Click on "Book Now – booxi"
Click "Add button"
Click "Connect".
You will be prompted to login to your Booxi account; enter your credentials.
Once successfully signed in, you will be redirected to your Weebly dashboard.
Under "Installed Apps", you’ll see the new option “Book Now booxi”.
Click and drag the Booxi button to your desired area. The button will display “No Api Key Configured”.
Open the button settings, and enter your API Key in the appropriate section (to find your API key, go to "My Business" > Business Details > "API key").
You can tinker with the advanced settings to fully customize your button.
Publish the changes and test our your button.