Expression evaluation error at function a!fromJson: The jsonText parameter was not valid JSON.) (Logic Output

Hi All, 

getting an error as below and flow is stuck at XOR gateway. Please advise:

Error:An error occurred while evaluating expression: =a!localVariables( local!statusCode: if( rule!APN_isBlank( pv!RMO_CDT_TxnLog.responseMessage ), "400", a!fromJson( pv!RMO_CDT_TxnLog.responseMessage ).StatusCode), and( or( local!statusCode = "0", local!statusCode = "200" ), pv!Result.statusCode = "200" )) (Expression evaluation error at function a!fromJson: The jsonText parameter was not valid JSON.) (Logic Output)

Code in XOR gateway:

= a!localVariables(
local!statusCode: if(
rule!APN_isBlank(pv!RMO_CDT_TxnLog.responseMessage),
"400",
a!fromJson(pv!RMO_CDT_TxnLog.responseMessage).StatusCode
),
and(
or(
local!statusCode = "0",
local!statusCode = "200"
),
pv!Result.statusCode = "200"
)
)