ERROR WHILE SENDING POST REQUEST TO PRODUCT IMPORT ENDPOINT

Greetings,

I am trying to send post request to productImportEndpoint after getting enactments from invoke URL. I am using app uuid, install uuid, instance uuid and install secret to create JWT, send Bearer token in headers and sending fieldDefinitions and dataSet in request body.

{

     "iss": "app uuid",

     "sub": "install uuid",

     "aud": "instance uuid",

     "exp": "current  time",

     "iat": "current time + 30 mins",

     "o.a.p.tenantId": "-tenant-id" 

}

signed with install secret which get from invoke url.

I am getting this error in response. Please help me in this asap.