New player help with Dark Knight interject ability

Fairly new player here, and I just got a fresh Dark Knight tank that I've been leveling on and off for maybe a week. I really like the Interject ability, but it doesn't seem to work.

I'm fighting an enemy and I see its channel bar going. I activate Interject well before the channel completes, but the enemy channel keeps going to completion and the enemy ability seems to activate. Interject will be on cooldown, so it definitely activated. In other games, when you interrupt an ability, the channel stops. Is FFXIV different?

I've done this in leves. I've done it with bosses in grand company squadron duties. I've done it to some extent with mobs in duties. In every case, it seems like Interject does absolutely nothing. The Dark Knight stun ability, however, does work. And it interrupts the channel like you would expect.

Am I interpreting the results wrong? Does the cast continue to the end, but the effect just doesn't happen?

Are there certain types of abilities or NPCs that are immune to Interject, and I just happen to be encountering them because of the type of content I'm doing?

Is there some prerequisite for using Interject?

Could it be some sort of lag? I've tested this by literally just doing nothing, with my mouse poised over the hotbar button, waiting for the enemy to channel something. Then I click it immediately. My ping time is about 100ms, so I don't see network lag as being an issue.

I've tried Googling this, but didn't find anything of use.

Please help.

Not every cast bar can be interrupted. A new feature introduced in Shadowbringers are cast bars that show when they can be interrupted - they'll be flashing red, which is your queue to use Interject. Non-flashing cast bars cannot be interrupted.

What you're experiencing with the 'stun' ability - I presume you're referring to Low Blow? - is an ability that imparts the 'Stun' status effect; this temporarily disables the enemy from performing any actions. Initially, its duration will be 5 seconds, but will drop to 2s on the second use, 1s on the third, and enemies become immune after the third time. Most bosses are immune to Stuns, outside of some older (A Realm Reborn-era) dungeon bosses; it's mostly useful for interrupting trash mob AoE abilities that can't be interrupted. There are also other abilities that inflict Stun - White Mage's Holy, for example, does so to all enemies in range, so it's excellent for large pulls.

Thank you. It appears that every time I've tried to use the ability, it was not an interruptible cast.

For anyone in the future who may have this same question, here is what the cast bar looks like, the difference being a red border for interruptible casts:

NON-INTERRUPTIBLE:

https://i.imgur.com/6opbDnl.png

INTERRUPTIBLE:

https://i.imgur.com/qkoRXwA.png

Quote:

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Originally Posted by ChadCloman

the difference being a red border for interruptible casts

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But more notably, the border is animated to draw attention to it.