[Gelöst] Cannot install neither OTGS Installer nor WMPL plugins manually ( WPML Multilingual CMS and string t...

Background of the issue:
I am developing a site and trying to install the OTGS Installer and WPML plugins, specifically WPML Multilingual CMS and string translation.

Symptoms:
When I try to install OTGS Installer, it says the plugin is activated, but it is not. When I manually install plugins, I receive the error 'The link you followed has expired.'
I cleared cache, I even turned off cache plugin, but its all the same

Questions:
What can I do to resolve the installation issues with OTGS Installer and WPML plugins?