The most common reason for this problem is that OS Property has size over 5MB
The File Size Upload Limit on your Server is set too low to allow larger files to be uploaded. By
default PHP allows files up to 2 MB, but you can set to 8 MB to get rid of this error.
If you have access to the php.ini, then change the directive upload_maxfilesize to "8M"
and reload the server configuration.
If you are running PHP in CGI mode on Apache, you can place an .htaccess_ file in your
Joomla! root directory and place the following code inside:
php_value upload_max_filesize 8M
This will solve the problem
You can also download this attachment, extract it, and copy file php.ini to 2 folders
root_of_joomla > administrator
and
root_of_joomla
After that, you can try to re-install OS Property.
You can download the custom PHP.INI file from osproperty.ext4joomla.com/php.ini.zip