Hi, com_phocagallery_ftp_install is not more used for Joomla! 3, see:http://www.phoca.cz/documents/16-joomla ... -in-joomla
Unfortunately, I cannot give any detailed information there, as components are not installed themselves. Joomla! - com_installer installs them, so if there is some problem:
- it needs to be solved in com_installer
- or on the server (memory limits, script limits, etc.)
Mostly the problem is with large components and limits on the server.
In case you get 404, etc. this can be caused by wrongly installed previous extension - in such case it is good to remove the extension (whole include its folders) completely form system and install it again.
See: http://www.phoca.cz/documents/16-joomla ... m-manually
I have solved similar problems after I have removed the component completely and newly installed (seems like Joomla! leave some info about the extension which then prevents from reinstalling it successfully
Sometimes, there can be problems while upgrading, see:http://www.phoca.cz/documents/16-joomla ... extensions
Installation problem solving:http://www.phoca.cz/documents/17-phoca- ... em-solving