We have the same problem. The certificate seems valid when the URL is entered to any standard browser (https://dub01.online.tableau.com/ - "verified by thawte, Inc.") but it fails when used through the API. We are using Java and this is the stacktrace I'm getting:
com.tableausoftware.TableauException: Problem with the SSL CA cert (path? access rights?)
at com.tableausoftware.server.ServerConnection.connect(Unknown Source)
Another things I tried (and failed):
o Using "sso.online.tableau.com" instead as that is the website url associated with the certificate
o Disabling all SSL verfication in the JVM (wouldn't be a long-term fix anyway --- but just for the sake of diagnosis)
Both attempts didn't work which leaves me to believe that the problem is somewhere in in the API/native code.