Welcome to the forum.
Depending on the make model of your optic it may be covered by a warranty. If it is a brand name check with them to see if they do any kind of warranty work. As mentioned Vortex has a no questions asked lifetime warranty. They will fix or replace the bad optic. If your optic is a cheap Chinese knock off you are probably better to trash it and buy another one.
The only place I am aware of that does any kind of work or refurbishment is vintage optics, but I only know they do traditional scopes, not sure if they do anything with electronic sights. As mentioned above, your best bet really is to reach out to the manufacturer as they usually have a service shop and will have the parts and knowledge to fix it right. Your best bet is to try any get it warrantied by the manufacturer, otherwise the cost of a repair/refurbishment of an electronic sight can quickly get into new optic territory, assuming parts can even be found.
It would probably be expensive if you did find a repair facility and finding parts would probably be a huge undertaking.
If your broken optics are not under warranty then you are probably out of luck unless the manufacturer does repair work.
If it’s just a cheap Chinese red dot. trash it. You get exactly what you pay for.
If you’re looking for something that can be repaired, you’ll need to spend more money on a quality brand that offers a warranty and service.
It's appears to be very difficult to converse with you so I kept it simple in my previous post. If you are able to answer those 2 simple questions it will tell us a lot but I have a lot more, let's call them optional questions and suggestions.
Are your original questions general in nature and hypothetical or does your red dot not turn on? If so are the batteries fresh and good to go? If it doesn't hold zero is it mounted correctly and solidly? Are the adjustment knobs solid? Would a dab of locktite help?
Did you buy it new or used? How much did you pay for it and how much are you expecting an average repair to cost?
I have a Burris Fastfire III that had a problem similar to yours. I sent it back to the factory for repair and they sent me a new sight (I've heard of others having similar results). Since these sights are tiny electronics I expect fixing is time consuming and expensive and I would expect that any sight with a price above $300 will (should) treat you similarly. Incidently, I have a couple of Tasco $40 Red Dots that are at least 14 years old and work just fine. Expensive sight shouldn't just stop working, and if they do the company should deal with it.
I have a Crimson Trace for my G19 that quit. I called them and was told it was their only model that didn’t have the lifetime warranty. They did offer me a discount on a new one but it wasn’t enough to interest me.