Can not get a certificate or plates

I am a disabled vet, and on social security disability and had a total knee arthroplasty lost my job lost health care. I have not been able to get plates or a certificate. I currently am seeing the VA for balance and falling issues which caused me to get the knee replacement. I was  told it is not severe enough to warrant the plates. I am paranoid about falling is this for real. How do I get plates.