I deleted the key from both your interface and out website.
I created a new key.
It registered successfully.
All seems to be working, other that the fact I can't activate the OTGS Installer plugin.
I'm glad to hear that the new key resolved the issue. Regarding the OTGS Installer plugin, it is only required when installing the plugin for the first time. If the WPML Core plugin (WPML Multilingual CMS) is already installed and enabled, the OTGS Installer plugin is no longer needed and will be automatically disabled.