When I try install Collabtive. I had a issue because cant read install.php (is a page blank).. the user had over access with chown and chmod... i follow perfectly all steps for installation and the requirements is more high than recommend...
Program Specs
OS: Linux Slackware
App:
Collabtive 2.1.1
PHP 7.08
Apache 2.4.23
MySql 5.1.45
Collabtive developer here. You should have a look at your error log file. This might give a clue about what went wrong.
My best guess: Though we have carried out successful tests with Collabtive and PHP 7, this combination is not yet recommendable. If you have the opportunity, please try out Collabtive with one of the latest PHP 5 versions.
If you need further assistance, feel free to ask for help on the official Collabtive support website: http://www.collabtive.o-dyn.de/forum/