Override external IP not inheriting from General Tab

We have 2 internet connections so that if one goes down we can switch our PBX over to the other one. In the old version of FreePBX, we could hit the “Auto Configure” button & everything would switch over just fine. Now when I hit the “Detect Network Settings” on the General tab, that works fine, but on the “Chan SIP Settings” tab, the external IP doesn’t update or inherit from the General tab as the help info says it should.