pH7CMS requires Apache "mod_rewrite".
Firstly, please make sure the ".htaccess" file has been uploaded to the root directory where pH7CMS is installed. If not, use your FTP client (such as Filezilla) and upload it again from pH7CMS unziped package and try again.
Secondly, please make sure "mod_rewrite" is correctly installed.
Click here if you want to get more information on how to install the rewrite module.
After that, please retry.