Did you also ensure that you've whitelisted all the locations that your web data connector is accessing using the secondary whitelist? As an added security measure, we ensure that your connector is only making requests to locations that you have also whitelisted.
More info can be found here: tabadmin commands
Hope that helps!
I'm also having this same issue described above. Is it possible to use wildcards when whitelisting WDC's? If yes, please include examples.