Snort not firing alerts

Question

I'm currently trying to setup snort on my remote ubuntu server (xenial). Therefore I installed snort via

apt install snort

and configured it according to my network. My machine has a static ip 176.9.103.111 and a netmask of /27.

Thus I configured my HOME_NET to be 176.9.103.97/27, as .97 is the beginning of my subnet, while .127 is the broadcast address. The service starts up just fine and no errors are given, however when trying to test my snort service by portscanning with nmap the IDS does not give me an alert.

My snort.conf is default except for the aforementioned HOME_NET variable, which I set manually.

When checking the status of the service ubuntu tells me that it is active and running and also listening to the correct interface and setting the correct HOME_NET

/usr/sbin/snort -m 027 -D -d -l /var/log/snort -u snort -g snort -c /etc/snort/snort.conf -S HOME_NET=[176.9.103.111/32] -i eth0

The log-file /var/log/snort/snort.log is binary so I tried opening it with snort -r which lead to the following:

root@guybrush /var/log/snort # snort -r snort.log 
Running in packet dump mode

    --== Initializing Snort ==--
Initializing Output Plugins!
pcap DAQ configured to read-file.
ERROR: Can't initialize DAQ pcap (-1) - unknown file format

Fatal Error, Quitting..

Does someone know, why my IDS is up and running but not alerting me, when I fire up nmap? What am I missing here?

I tested this in a KALI Linux environment before to learn about the snort configuration and that worked beautifully. There I set up a VM running Kali and snort and when running nmap against the VMs IP address from my host machine the IDS told me there was a potential attack going on, so I was confident enough to try setting it up on a live system.

Any help is appreciated.