Hello,
A malfunction can be caused by two factors either definitions missing or additional packages missing.
I would start by checking if the reverse proxy is working by downloading one of these files below. In SEP12 there is the fallback option and it should use symantecliveupdate server from the internet (over 80 port) along with Your defined Revers Proxy server in LiveUpdate policy. I think in SEP 14.x this fallback option is not working You need to add additional LiveUpdate server in Your policy :)
ht*p://your_SEPM_server:8014/luproxy/minitri.flg
ht*p://your_SEPM_server:8014/luproxy/masttri.zip
Check LiveUpdate logs for more info.
Additionally please check if these packages are existing in OS or just run these command below :)
yum install glibc.i686 glibc.x86_64 libgcc.i686 libgcc.x86_64 libX11.i686 nspr gcc bzip2 kernel-devel kernel-headers