Add Record in Leads, but missing data

Add Record in Leads, but missing data

Hi all,

I'm pushing a Leads record as json via the API. This is my request with some custom fields:

{
   "data":[
      {
         "Lead_Owner":null,
         "Salutation":null,
         "First_Name":"FirstName",
         "Title":null,
         "Last_Name":"LastName",
         "Company":null,
         "Lead_Source":null,
         "Industry":null,
         "Annual_Revenue":null,
         "Phone":null,
         "Mobile":null,
         "Fax":null,
         "Email":"test@myemail.com",
         "Secondary_Email":null,
         "Skype_ID":null,
         "Website":null,
         "Lead_Status":null,
         "Rating":null,
         "No_of_Employees":null,
         "Email_Opt_Out":null,
         "Campaign_Source":null,
         "Street":null,
         "City":null,
         "State":null,
         "Zip_Code":null,
         "Country":null,
         "Description":null,
         "Algemene Website updates":"true",
         "Website updates omtrent design":"true",
         "Website updates omtrent mode":"true",
         "Type":"Nieuwsbrief",
         "Datum":"18\/05\/2020",
         "Omschrijving":"Popup",
         "Taal":"Dutch",
         "Sector":"audiovisuele industrie",
         "Source opt-in":"websiteformulier"

}

],
   "trigger":[
      "workflow",
      "approval",
      "blueprint"

]
}

I'm also getting a succes 'record' added response.

But most of the custom data is missing.

How should I check what's going wrong?