First, what breed do you have? Some breeds can be more difficult to potty train.
Secondly, is your dog fixed? Male dogs especially are prone to “marking” in the house if they aren’t potty trained, but some females do it too.
Is this a new occurance, or is it something she’s never quite gotten the hang of? Do you have some way for her to let you know she need to go out, (bells on the door for her to ring, or teaching her to sit by the door, or to bark, or to come get you, etc)? Have you ruled out a medical reason for her soiling?
DO NOT punish your dog if you catch the accident and not her actually in the process of soiling, (it doesn’t sound like you are, which is good). Dogs associate discipline/reward with what they are doing at the time, so if you find the puddle and scold her while she’s just sitting there, she won’t understand that you’re upset about the puddle and not about her sitting there.
I would go back to basics with your dog. If she’s not able to in the same room as you are, she should be crated. When she is able to be in the room with you, keep an eye on her so you can watch her for signs of imminent pottying and hurry her outside. If you catch her in the act, tell her “No!” and rush her outside. When she goes outside, praise praise praise.
If she doesn’t already have a “potty” word, teach her one. While she is in the process of ‘going’ outside, put the word you want to call it to the action. For example, we use “go potty” to mean pee, so while our dog was peeing, we would tell him “Go potty!” and then “Good boy! Good potty!” and keep repeating it until he had finished, then give him pets/praise.
Thoroughly clean your floors with a cleaner like Nature’s Miracle that removes the scent of the accident. Just because YOU can’t smell it doesn’t mean she can’t, and lingering traces will only encourage her to resoil. Also, make sure it is a cleaner specifically for this purpose, because some cleaners contain ingredients that smell enough like an accident to encourage them to soil.
Do you feed/water her on a schedule? If not, it might be a good idea to do so. When you know when the stuff goes in, you’ll learn when it needs to come out.
Take her out on a schedule, too. Every two hours if she’s not in the crate. As she improves, you can increase the time between her potty breaks.
Hopefully these tips will help you out! We’ve done foster care for several dogs, many of which weren’t 100% reliable. These tips have worked for almost all of them, so maybe they’ll help you, too.