Hi @jonathanstegall
i tried same on PostMan Rest API client, i got a success response.
url : https://xxx.my.salesforce.com/services/data/v48.0/sobjects/Order_Time_Slot__c
Body
{
“Start_Date_and_Time__c”: “2020-10-10”,
“End_Date_and_Time__c”: “2020-10-10”,
“Parent_Order__c”: “8010p000001eBlNAAU”
}
Response
{
“id”: “a0C0p000000jzL7EAI”,
“success”: true,
“errors”: [],
}