The introduction of Clarion 9 has seen support for *.sdaddin packages removed

What this means is that you can no longer use the built-in AddinManager to install, update or remove 3rdParty addins. (For further details, please see PTSS#39923 - login required)

Additionally, this breaks the “web-update” feature of the AboutClarionAddins addin. See the other topics in this category for workarounds.