In the past, it was possible to use 1st generation Buttons (R9861006D01) with 2nd generation Base Units (CS and CSE range) and to use 2nd generation Buttons (R9861500D01 and R9861500D01C) with 1st generation Base Units (CSM, CSC). Since firmware 1.8, this is no longer possible as the 1st generation Button has reached the end of its lifetime and has not been found to be secure enough to deliver the CS and CSE standards. This means they will no longer receive updates, meaning new functionalities will not be available and issues will not be solved and compatibility between these two generations has been disabled, meaning they can no longer be paired or used between generations.
The 1st generation Buttons were shipped and sold with CSC-1 and CSM-1 Base Units and can be recognized by looking at the layout & info on the sticker at the back. More info on how to identify your Button and Base Unit as well as an overview of which Button works with which Base Unit can be found in [KB6454]
Firmware v22.214.171.124 for CS(E) ClickShare models has been released on July 2019.