There are kind of registration errors that really hard to debug. Usually they appear in error logs as Plug-in assembly does not contain the required types or assembly content cannot be updated.
Reasons causing the error could be different:
- Plugin get removed;
- Plugin get renamed;
- Plugin's access level modificator has changed.
But result is always the same: assembly could not be registered, since required plugin type is missing due to one of caused mentioned above.
Now this errors detected in PluginRegistration automatically. The code checks plugins listed in given assembly and in the CRM organization and in case of mismatch shows user list of plugins that causes the problem.