When I go and put it into gear it doesn't go.

I put transmission oil in it and let it run and shifted the gears like I am suppose to and it worked for about 10 miles and after that nothin put it into gear and it doesn't what to go. I don't even feel it shift into gear, no gear at all. Thought maybe the transmission went but now IDK I'm thinking maybe the torque converter. I'm no mechanic but a daughter of one an unfortunately daddy pasted away so I need your help. What do you think? I'm sorry I can't donate to your cause but would appreciate your opinion.