It would surprise me if the control was seen if not in setup mode in the previous version. Perhaps you can elaborate on what is wrong assuming that it is not wrong that you only see the control when in setup mode?
I reinstalled MIPSDK_Redist_Installer_x64_2020R1.msi dotnet 4.6
and the plugin works 100%, without entering setup on a Milestone 2020R2 server. But with the 2020R3 sdk installed, the plugin does not work (on a 2020R3 server) until I go into setup and tab through the values and exit setup (then the 2020R3 compiled plugin function correctly).
We are not trying to “view” properties, but just have the plugin use the values. Definitely, no changes where made except recompiling for 2020R3. (We are also having trouble with other plugin(s) since the upgrade to R3 also.)