/mtc/event return { "success":0 } and no tracking shows in Mautic

Your software
My Mautic version is: v2.16.0-beta
My PHP version is: PHP 7.1.27-1+ubuntu18.04.1+deb.sury.org+1

Your problem
My problem is: Using the WPMautic plugin. /mtc/event returns { success: 0 } and there is nothing shown in the Page Visits graph in Mautic

I am using an Apache Reverse Proxy in front of Mautic to add SSL. I suspect this is the problem but should not be I think. Here is the config from Apache:
<VirtualHost *:80 *:443>
SSLEngine On
ServerName mautic.ourserver.com
DocumentRoot /tmp
ProxyPreserveHost On
ProxyPass / connectiontimeout=5 timeout=30
ProxyPassReverse /

These errors are showing in the log:

Steps I have tried to fix the problem:
Tried to add CORS settings for the domain, but this does not seem to be a CORS error since those usually show up in the browsers developer console

Hi @jensolsson did you solved the problem ? and how ?