Dynamics CRM 2011 on premise.
We have had a plugin registered for a few months. It was referenced by a solutions in two organisations and I could see it in Solution > Components > Plug-in Assemblies in each organisation.
Yesterday I noticed it was not visible in this view. The Plugin Registration Tool shows it still installed.
I unregistered it using the Plugin Registration Tool and then registered it again but it still isn't visible in the solution that references it in either organisation.
How can I investigate this?