I am getting this exception when trying to publish out my survey.
I have checked an I do have a server validated under My Organization> Settings>ServerThe certificates are not causing issues either.
I'm unsure based on the description. Here's a good blog that discusses how to configure your mobile device to proxy through a tool called 'fiddler', which will help examine your web traffic and perhaps point to where the fault lies. It does look like a bad request somewhere.
Configure Fiddler to Capture Web Traffic from an iPhone/iPad | Support Services Blog
Whenever I've seen that error it's because Portal doesn't trust the certificate Server is using for the Admin URL. If you check the Portal logs, you may see an error indicating the certification path is not trusted. Another way to check is through the checkURL resourse:
If that does not return a 200 response, follow this doc to import the certificate for the Admin URL into the Portal to trust it.
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