I configured jenkins in spinnaker as follows and setup spinnaker pipeline.
jenkins:
# If you are integrating Jenkins, set its location here using the bas
According to Jenkins Directive First you have to check your Jenkins version if the version is < 2.176.2 then per Jenkins guideline CSRF tokens (crumbs) are now only valid for the web session they were created in to limit the impact of attackers obtaining them. Scripts that obtain a crumb using the /crumbIssuer/api URL will now fail to perform actions protected from CSRF unless the scripts retain the web session ID in subsequent requests.
Alternatively, you can install the Strict Crumb Issuer Plugin which provides more options to customize the crumb validation. It allows excluding the web session ID from the validation criteria, and instead e.g. replacing it with time-based expiration for similar (or even better) protection from CSRF.
Steps :
It should work now.
Check this image for your reference