If you try to install on Joomla 3.5+, there's a problem.
It's because component's installer script doesn't know Joomla! 3.5.
You can manually fix it by changing the file script.php within com_jem.zip inside the package (yes, inside the zip inside the zip - sorry
Change line 212 from
if (!(($jversion->RELEASE == '3.4' && $jversion->DEV_LEVEL >= '0') ||
if (!(($jversion->RELEASE >= '3.4' && $jversion->DEV_LEVEL >= '0') ||
(allow 3.4 or greater) and then recreate the component and package zip files.
In the coming JEM 2.1.6 this will be resolved