This question is not accurate enough, the actual problem is described here: https://www.telerik.com/forums/radtoolbartray-itemtemplateselector-problems
I have not updated my Telerik components for years; last time I did, the radToolbars stopped working, and I have not had the time to look into it. So I reverted back to what worked, but now I feel it's time to get back on the track.
So here we go: programmatically generated toolbars on my main form do not display any buttons. I use toolbar and button view models that the UI components bind to. The entire set of toolbar viewmodels are built on the fly, and only empty toolbars show up. I have other UI components which have buttonless toolbar components placed onto them at design time, and those work when I add the buttons runtime, so the only difference I've found has to do with the non-working toolbars not existing at design time.
They work in RCWPF 2018.3.1016.45, so that's what I'm still using. This happened when I (briefly) upgraded to 2020.2.513.45, and the problem still exists in the current version.
The images show the two different versions. The dockable Conceptual model window contains an empty-at-design-time toolbar, which is populated when the UI is initialized. The main window contains a toolbar container which does not contain any toolbar components at design time.
Does anything come to mind immediately? If not, I will dig into my code.
And to be clear, the generated toolbarviewmodel has several buttonviewmodels on it. The same code builds the viewmodels in both cases.