Dog moms, please help!

I wasn't sure where to post but I know there's lots of dog moms on this app who could help! I adopted my dog a year ago. She is around 3 years old. I adore her! Her previous owners said they were still working on potty training. They hadn't had her long, she actually got dropped in their yard. Anyhow, I still can't potty train this dog. She never alerts when she needs to go out. She just goes in a corner somewhere and we find it later. It's so frustrating. If we take her out right after she eats, she won't go. 20 minutes after she's ate, she's already went in the floor. EVERY night she goes in the floor while we sleep. Sometimes we take her out and an hour later she's already went in the floor. We try to take her out constantly but I swear this dog CAN NOT be potty trained! What else is left to do?! I feel like I've exhausted all my efforts and I've never had this issue with a dog before!