Help with wiring

My switch box completes a circuit for my lights. My lights are wired at the fixture. Can I still use this switch? Or do I need to do some rewiring? Trying to install the red switch

Do you only have two conductors (plus possibly a ground) going into your switch box? It’s sounds like you are describing a non-neutral, but the information is a bit vague.

I believe my fixtures are wired in the attic. Then a I line separating the hot is run to the switch box. I have the black in line and white in load. Tapped a neutral off of another line in the same box that are currently combined. Black and white joined so lights are permanently on currently.

The lights turn on and off while the inovelli clicks and cycles led colors

I’m not exactly sure what you’re trying to say. In the first paragraph you said the black and white are joined together so the lights are on permanently. In 2nd paragraph you talk about the lights going on an off. Are you trying to say that when you unhooked the black and white and wired them to the switch that’s what happened? It’s hard to understand exactly because in your first post you just asked if you could use a switch in that configuration.

So you didn’t answer my question, but I’m going to assume that there is only a 2-wire Romex (not counting the ground) coming from the light and those two conductors were both connected to the dumb switch and no other conductors except the ground are involved.

So this is a classic non-neutral configuration. You’ve figured that out because you’re trying to add an unrelated neutral to the mix.

1 - You shouldn’t add an unrelated neutral. Even though it’s in the same box, is it on the same breaker? That’s unlikely since if that light was on the same circuit the electrician would have started the leg in the box, not the light. If that’s the case, sharing a neutral is improper and at least in the US, violates the NEC. There is a safety reason you should do that.

2 - If the neutral is on the same circuit, disregard #1, but I don’t know that’s the solution. Others have tried and there always seems to be an issue with it working correctly. I don’t know the Inovelli internals well enough, but my suspicion is that borrowing a neutral, same circuit or otherwise, is bad or causes issues.

So you have a couple options:

1 - Instead of a switch, use a dimmer. It works in a non-neutral configuration. If you don’t want it to be a dimmer, you can put it in the Smart Bulb Mode and it will work like a switch.

2 - Switch the circuit the light is on. As long as you can get to the light box, this is easy. You already have a hot and neutral (presumably) in the switch box, so use that to start the leg. You’d wire the hot and neutral to the switch and send the load (switched hot and neutral) to the light via the existing 2-wire. To do this, you need to get at the light box and cap off the incoming hot (or just send it downstream if that’s what it’s doing), eliminating the light from that circuit.

With a hot and neutral in a 2-way configuration, you shouldn’t have any issues.