My 4 year old isn’t potty trained?

rose

She turns 4 in two weeks.. still isn’t potty train. She tries sometimes but still uses diapers. Not really sure what to do. My mom says she’s been really trying and has been trying different things but they’re not working. Any suggestions? I’m worried that maybe there’s something wrong?? I haven’t been home or seen her in nearly 8 months (military)but, before I left she was starting to recognize and vocalize she needed to go.