Did you want to post in the LYNC / Skype for Business section and if yes how did you upgrade the phone?
The Cab File upgrade was only added in UC Software 5.0.0 so I cannot imagine this being the case. In addition there is no software 4.3 as we have 4.0.x and 4.1.x and then went to 5.x.x
Please provide more details and correct firmware versions.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's