Subscription PATCH Call not working for updating a value at subscription level

Summary:

Unable to update value of attribute "XX_OSS_RemainingChillers_c" via REST API both via groovy. Getting error " Invocation of service URL used in connection failed with status code 411 Length Required."

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):

        def headers4 = ['REST-Framework-Version':'8']
        def Payload = [XX_OSS_RemainingChillers_c:finalVal]
        WService4 = adf.webServices.XX_OSS_UpdateRemainingChillers
        WService4.requestHTTPHeaders = headers4

After adding header as → def headers4=['Content-Type' :'application/json','Content-Length':'4094'] then also error was coming.