All right... let's have a little look here. I'll try to focus on what you're doing that'd impact performance on Tapas specifically.
First off, you're in a bit of a tricky genre making what sounds like a crime thriller in the "Drama" section where I feel like a lot of the content is more relationship drama. It's possible it'd immediately get a boost by moving to "mystery" or "action" or something. Just overall though, a serious gritty crime thriller with a very bold, lurid art style is always going to have a smaller audience on Tapas than other works of a similar quality based on the kind of audience the platform draws.
So right off the bat I can see an issue that'd put people off. The cover. The title is way too small to be comfortably readable when viewed on the app and it's pushed way up at the top without enough padding, which tends to make it look a bit unpolished. The style of the cover doesn't reflect the aesthetic of the interior pages, which are actually more colourful than this might lead somebody to believe. Finally the design of the cover just doesn't really spark excitment or clearly illustrate what the story is about. It's a bored looking guy standing in front of something... a wall? (I can't tell what it is) and then there's this shadowy, barely defined generic evil guy in the background protagonist is not really engaging with, and a cityscape that's barely visible due to low contrast and how small it is overall.
I'd recommend going back to the drawing board and giving your cover some love, think about how you can make it look really dynamic and punchy, engage the reader and illustrate very clearly "this is a thriller about hitmen fighting a serial killer with a bold aesthetic that uses really bold colour combinations."
Also, make a banner. There's really no good reason I can think of not to; it just adds polish to the page. Unique thumbnails for updates wouldn't hurt either in terms of just making it look like you care about your comic and presenting it nicely.
I'd recommend maybe starting with these things first.
The pacing is a bit on the slow side for Tapas, which may be another reason it doesn't have huge traction. Popular Tapas comics tend to get the plot moving very fast. Still, that's more of a thing to think about in future comics or if you decided to reboot than to necessarily go back and fix in the existing comic.
I think the key thing to remember is that when putting a comic on Tapas, if you're going outside of the most popular genres and tropes but you still want to build an audience, you need to compensate by making the presentation as polished and appealing as you can, and the storytelling as engaging and accessible as you can. It's always an uphill struggle when you choose to go outside of stuff like romance and relationship or Fantasy stuff.
