I'm using php-curl to add rows to a sheet throught POST requests and it works good to fill all the text fields. 
But when I try to add data for a column that has PICKLIST as type it won't work.
 
So this is how the column is structured.
 
{
         "locked" : true,
         "type" : "PICKLIST",
         "index" : 5,
         "title" : "Severity",
         "lockedForUser" : true,
         "width" : 134,
         "options" : [
            "Critical (Systems are down and no workaround is available)",
            "Major (Functionality is severely impaired)",
            "Medium (Partial/non-critical loss of functionality)",
            "Low (General usage questions. Productivity not impacted)"
         ],
         "id" : 5506789081933700
}
 
This is how I try to add data to for that column
 
"{"columnId": 3713640235853700, "value": "Critical (Systems are down and no workaround is available)"}"
 
I also tried to use ' "value": 0 ' and ' "value": 1 ' as I thought I maybe need to add the index of the array. But that didnt work either. 
 
This is the error I'm getting.
{
  "errorCode" : 1039,
  "message" : "Cannot edit a locked column 5506789081933700",
  "refId" : "erk4rwsf3uyq",
  "detail" : {
    "index" : 0
  }
 
 
So please, what am I doing wrong ? Thanks