Great! I’ll try to reproduce your problem, but I only have a windows 8 and QGIS 3.2.0.
EDIT: I have no problem running it with this configuration.
EDIT2: Problem identified with QGIS 3.4.4
EDIT3: The issue is on the qgis_otb_cli.bat file. The variable OTB_LOGGER_INFO introduce a bug and prevent the plugin to work correctly… This bat file is regenerated by QGIS every time, so we need to modify how it is generated by the otb plugin.