yum -y install http://package1.sangoma.net/distro-upgrade-18041807-1.sng7.noarch.rpm
This will attempt to re-run the upgrade script. It will try harder to resolve any issues that may be found, and will be more verbose with errors if it can't.
If the failed upgrade script does not repair your machine, please open a ticket at issues.freepbx.org and attach at the very least the following log files:
Most problems can be solved by running 'yum update' and reading the errors. If there is an error about 'AAA conflicts with BBB, in package from XXX', you can simply 'rpm --erase --nodeps XXX', and run 'yum update' again.
If you can not solve your problem, you will need to post the errors on the FreePBX Forums.