There are some people who just can't match a pitch, no matter what they do. They are rare, fortunately.

We don't know whether you are one of those, or whether the shortage of music in your life is the problem.

I suggest you do two things: play recordings of vocalists you like and sing along with them as you work around the house or drive in the car. Just don't imitate rock & pop singers who bellow and blast, abusing their voices. (I'm sure you have had enough training to recognize what is really bad.)

Join a choir or similar group. Sing softly at first if you are worried about being good enough.

I bet it's just a muscle problem. Your singing apparatus needs to get strong enough and co-ordinated enough to actually do what your brain/hearing are telling it to do.