We have a couple users that have the dropbox desktop client. We have a transparent proxy running on our network as well which does deny access to dropbox for PII compliance. We make exceptions for users that need it. We set it up as having the proxy settings on the client to manual with our proxy IP entered with the port 8080 and http dropdown selected. Authentication settings are not used as authentication to the proxy is done via AD on the machine. Then we set up policy to allow the users to connect to a list of dropbox urls in order for the client to work. It has worked fine until these users updated to this version. Doing packet captures doesn't reveal any new connections to new URLs or anything related to dropbox being dropped. Our proxy does SSL packet inspection. I'm thinking it may be related to a certificate issue but I'm not sure. I hope someone here may have some insight?
(Bypassing the proxy allows the client to sync. The issue is 99% likely related to the SSL inspection.)