Problem in integrating with Box with Box File Utilities Plugin

Hi

I am trying to integrate Box with Appian using the Box File Utilities Plugin. I have created a JWT App in Box, and added the Private and Public Keys, and also uploaded the PEM files in Appian. However, when I am trying to create a token by createToken method, it's throwing the following error - 

Error creating JWT

Here is the error details from log - 

2019-01-25 18:55:17.857 INFO [ajp-nio-8009-exec-3100] org.apache.catalina.core.StandardWrapperValve.invoke Could not reconstruct the private key: java.security.InvalidKeyException: invalid key format
2019-01-25 18:55:17,810 [ajp-nio-8009-exec-3100] ERROR com.appiancorp.ps.plugins.boxFileUtilities.jwt.CreateJWT - Error creating JWT
com.auth0.jwt.exceptions.SignatureGenerationException: The Token's Signature couldn't be generated when signing using the Algorithm: SHA256withRSA
	at com.auth0.jwt.algorithms.RSAAlgorithm.sign(RSAAlgorithm.java:63)

Following is the rule I am using to get the token - 

fn!createtoken(
privateKey: cons!BOX_PRIVATE_KEY_FILE,
publicKey: cons!BOX_PUBLIC_KEY_FILE,
sub: cons!BOX_USER,
customClaims: "user",
kid: cons!BOX_PUBLIC_KEY_ID,
iss: cons!BOX_CLIENT_ID
)

Thanks much in advance.