500 Error connecting to http://<DA_Proxy>:8500/ui/
And also errors in the consul-ext.log
2019-06-24 21:46:03 WARN Main:267 - Consul servers are not available. Keep wating.
PM 3.7
There were 2 Interfaces on the systems, and consul.service was binding to the incorrect interface
It was binding to 172.x.x.x instead of 10.x.x.x
Edit the /etc/systemd/system/consul.service on DA_Proxy, DA1 and DA1, changing the 172.x.x.x address to 10.x.x.x
Then restarting the consul.service
systemctl daemon-reload
systemctl stop consul.service
systemctl start consul.service