Generating JWT token returns{"error":"invalid_grant","error_description":"Signature verification fai

Hello,

I'm generating a JWT token and I'm getting this error 

{"error":"invalid_grant","error_description":"Signature verification failed"}

These are the client id and enterprise id. I'm not gonna post the secret or the key for obvious reasons.

```

ClientID: 0g635tmvnxylfkuzfi2j726au6nhk48f
EnterpriseID: 7249580

```

My code worked for different account - as in generated the proper token. When I tried it for a different client id and client secret (and using the proper public/private keys) I started getting this error. 

I've read this - https://developer.box.com/v2.0/docs/authentication-with-jwt several times to make sure I didn't miss anything. I've authorized the app and "Generate User acess tokens" is set to true. 

Any tips?

Alex