Service Unavailable

php did not respond properly to the request

the root cause of this error is often slow php code

service unavailable

as a result

srv/users/sysuser/log/appname/appname_apache.error.log

you should disable any plugins the app is using

srv/users/sysuser/log/appname/appname_phpx.y.error.log

srv/users/sysuser/log/appname/appname_phpx.y.slow.log