Hello,
Apologies for the inconvenience caused!
We have checked out your Website and you are using an Old Version of Canvas which has Old 3rd Party Plugin Codes that could cause conflicts with the OS Updates. Make sure that you are using the Latest Version of Canvas with the Updated Codes to ensure maximum compatibility. This is why we always keep Canvas updated with the Latest Plugins and Codes.
Additionally, there is one JS Error in the console after BigSur Update which is related to a 3rd Party Plugin, which we will update and release shortly in a few hours. So simply update to the Latest Version and this will definitely fix your issue.
Hope this Helps!
Let us know if we can help you with anything else or if you find any further issues.