Assets in a Content-Only plugin enabled in a Blueprint-only project cannot be loaded when the project is packaged. If a Content-Only plugin is enabled in a code project, the assets in the plugin are loaded successfully when the project is packaged.
The message from the Print String node is not displayed. In the log file, there is an error message stating that the Blueprint could not be loaded.
The Blueprint loads successfully and the message from the Print String node is displayed.
Add a code class to the Blueprint-only project to convert it to a code project.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-62969 in the post.