A character having rank 3’s doesn’t mean that character will receive Echoes. In order for a character to receive Echoes, there needs to be Rank 3 Essences you do not possess but you are eligible to purchase. In order to be eligible to purchase a Rank 3 Essence, you need to have unlocked at rank 3+ that same Essence, or one from the same source, on any character on your account, and the current character must not yet have that essence at Rank 3+, and that Essence must be for a role your character can perform.
As an example, if your main is a pure DPS (so only eligible for pure DPS Essences), and there are no Essences that your alts have gotten to rank 3 but your main has not, you won’t get Echoes, because you wouldn’t be able to purchase anything with them.
Does that make sense?