provided by Star2Billing S.L.

I downloaded the latest version of a2billing and installed it on CentOS 7 with Asterisk 13. But I'm getting this error when I tried to access the admin page on my browser after installation.

=====ERROR=====

[Fri Mar 02 03:50:44.545176 2018] [:error] [pid 1133] [client 10.32.1.32:4128] PHP Warning: require_once(/usr/src/a2billing/common/lib/../../vendor/autoload.php): failed to open stream: No such file or directory in /usr/src/a2billing/common/lib/admin.defines.php on line 33
[Fri Mar 02 03:50:44.545234 2018] [:error] [pid 1133] [client 10.32.1.32:4128] PHP Fatal error: require_once(): Failed opening required '/usr/src/a2billing/common/lib/../../vendor/autoload.php' (include_path='.:/usr/share/pear:/usr/share/php') in /usr/src/a2billing/common/lib/admin.defines.php on line 33

=====ERROR======

Please what am I doing wrong?