We have a version of our product in the wild, released as a Managed Solution with a Plugin Assembly.
Since this release, we have developed new Plugins added to the existing assembly.
However, when attempting to upgrade the Managed Solution while using the import option to Maintain Existing customizations, the import fails and claims that either there is a missing type from the Plugin Assembly or else that the Plugin Assembly is not updatable. (The trace log is loquacious but says nothing more meaningful.)
I have tried bumping the solution and assembly versions to see if CRM is perhaps being picky about how I version changes; neither has made a difference.
Since I dev with Unmanaged Solutions, I was surprised to see this; and I’m out of ideas, since reflector confirms that both my deployed assembly and newly compiled ones expose the same types (plus the ones added to the new one).