Because that's what the exception says according to you. Here is a link that shows how to unlock such sections. I must note that this exception is related to your IIS installation and not Radzen.
Also the WebDAVproblem does exist, Radzen users have reported it and this is why that section in the web.config exists (<remove name="WebDAVModule" />) . Microsoft even documented it.
I give up. The issues discussed in this thread are not related to Radzen but we fail to convince you despite the links we provide. You could have searched online for the last message to see that it happens when the IIS process may not have write access to the app directory to create the log file. You could have also just removed the logging attributes altogether.
It seems that our product and the support we provide do not satisfy your requirements. I am afraid this is the best we can provide. We have no other option but to refund your Radzen subscription.