Unable to install "SqlServer Management Studio Add-On"

Hi!

During the issues with https://forum.devolutions.net/topics/52613/unable-to-start-rdm , I re-installed RDM to see if it was an issue on my workstation only (turned out it was a general problem on your side).

Now, every time I change something (adding, deleting, renaming entries or also change something like a password), I get the following popup window:


When I click on "Install", another window appears, telling me that this Add-on isn't available:


The modifications itself behave in a strange way, sometimes they are saved (after clicking on "Ignore"), even visible after a restart of RMD - sometimes they are not - and sometimes they are only visible for me as long as I am in the session, but are gone after a restart.

Can you please tell me where I can find this ZIP file and how I should install it (where to put its content)?

We're on RMD 13.5

Thanks!