In 4.17, attempting to open a project that contains a plugin with a missing .dll file results in a dialog box appearing that says that the plugin is not compatible with the current Engine version, and asks if you want to disable it (see attached Compatible.png). Clicking Yes disables the plugin and opens the project in the Editor, but this may not be what the user wants to do. Clicking No results in a second dialog box appearing (see attached Rebuild.png). The second dialog box states that the plugin is missing a .dll file and asks if you want to rebuild it.
The second dialog box is more likely to be the option the user wants to see, but clicking the wrong option in the first dialog box will prevent the user from seeing the second one.
Yes. In 4.16, only the second dialog box appeared in this case. The first dialog box appears to have been added in CL 3386999.
A dialog box is displayed stating that the plugin is not compatible with the current Engine version, and asks if you want to disable it.
A dialog box is displayed saying that the plugin's .dll file is missing, and asks if you want to attempt to rebuild it.
Head over to the existing AnswerHub thread and let us know what's up.