For future reference, you can pass -n to tcpdump, and it will display IP addresses and port numbers instead of names.

Right after PCAP Filter Set and SessionRequest detected, you should see Zone: Entrycode Client, and then it should try to load the map. If you're not getting that, then it's not seeing the zone entry packet.

The 'Giving up on finding arq nnnn' implies SEQ isn't getting all the packets. If you look in the FAQ at the root of the source tree, question 5 goes into this and suggests possible fixes. Basically, you need to either reduce the non-EQ packets getting to your SEQ system, or you need to increase your SEQ system's ability to handle packets (or both).

This could be why you're having issues getting spawns, though I'd expect it to work somewhat intermittently rather than not at all. But since you're seeing that message, I'd start there.

Other questions that might help - How beefy is your SEQ box? How saturated is your network? Are you trying to use SEQ on Live, Test, or TLP?