Check the Devices that are not configured in ACS report under Common Services > Device and Credentials > Reports. When integrated with ACS, all of the devices you wish to manage with LMS MUST be TACACS+ clients of the same ACS server. As long as a device appears in this report, it will not be manageable by LMS.
As for device selector changes in LMS 2.6, we have made the device selector more powerful. Device type views are still available (and should be enabled by default). Check your settings under Common Services > Device and Credentials > Device Selector Settings, and make sure the category types you want are enabled.
