HEC configs are in $SPLUNK_HOME/etc/apps/splunk_httpinput
Did you check that you turned HEC back on in the Global Settings button after reinstall? I believe you can create tokens and not have the option "on".
I have checked that the HEC is turned on in the global settings, I have two tokens created. But currently only the one token works and the other token gives me a 404 error - both are configured the same.
Are there any other setting that I am missing?