JMS Multisites is a package of 2.8 MB that is sometime difficult to install on server that does not allow to upload large files.
Parameter that can affect that (an not limitative) are :
upload_max_filesize
post_max_size
max_execution_time
When this happen, you can try installing from a directory like explained in the video
tutorial.jms2win.com/joomla/multisite-12...stall-from-directory
When you have a "blank page", this might be the symptom of a permission error.
In this case, you can search in a "error_log" file the reason of the error.
Permission issue, can sometimes be solved when using the joomla "FTP Layer" to ensure that all files and folders are owned by the same users.
So check also the ownership of the files and folders.
Some environment may have different owners of the files and folder. In this case, this is the symptom of a wrong HTTP Server configuration. In this case, contact your hosting company.