Solution
As of September 2016, both CX 555 and 755 became End of Feature support in accordance with Riverbed software support policies. This means that it will not be possible to install RiOS 9.5 or greater to either CX 555 or the CX 755 appliances. Therefore, please note, the latest version of RiOS that supports these models is 9.2.3.
This is also detailed in the release notes and other technical data related to release of RiOS 9.5.