I have no Assassin signals for The Sentinel Part 1

[Ed Edd & Eddie]

The condition for full sync in this mission is to use the Assassin signal at least once. There's just one problem, I Have no Assassin signals. I used my first during a templar den fight and he ended up dieing. After getting around to The Sentinel, that assassin that died was somehow resurrected and was level 10? so I appointed him to the leader of a den. I guess that means I can't use him anymore, because now he is not available to use.

TL;DR don't use your first assassin flag until you can recruit more

[mbutton15]

I'm hoping that if you check your map you will see (if I remember correctly) lots of 'plus sign' type indicators. These should indicate citizens under attack. Go and rescue one of them and then hopefully you should get your Assassin Signals back.

[Ed Edd & Eddie]

No they are not available until after this mission. So my point is just don't do the above so you don't have to redo the mission after you have acquired some more Assassins

[Goose]

I think you need to have more than 1 assasin recruit, and they are definitely available before this... you can see screenshots on IGN with full 3 bars (Arrow storm) available during this mission, so you probably just started it without doing other stuff first. I had a full 3 bars by this point too.