are you upgrading from a non-dsa build? If so, you may have to update your configs in /etc/config for the change. Not sure exactly what tho as i've been using dsa for a while now.
EDIT: From a community build for the r7800, i used this to get started with what needed to be changed for DSA config migration. See also the "mini-tutorial for dsa network config." This is from some time ago and likely not entirely relavent for your device. Luci seems to do a good job so perhaps just start with a totally new config - just do the basics first and work your way into it. I find dsa easier than swconfig but i might be... different.