Good Morning! Anything new I have problems with mikrotik too.
I had a similar problem as you but got it working (finally)
The problem was that I filled in the router's ip in knownlinks instead of the gateway ip. Check with tcpdump where the packages originate from (gateway or router ip)
Make sure mikrotik is using netflow V5 and NOT V9 and port 9996 (or whichever you prefer)
I'm using this line to start it:
perl asstatd.pl -r /opt/AS-Stats/rrd -p 9996 -P 6343 -k /opt/AS-Stats/conf/knownlinks -a 42337 -n -m /opt/AS-Stats/perl-ip2as/tools/ip2asn.json
It didn't generate rrd's without the ip2asn.json included. I used the openbsod fork.
I'm now facing an issue with sampling rate which seems to be off.. and mikrotik is unclear about the correct rate so it's guess work for each of our uplinks (depending on traffic volume)