You are accessing wrong URL. Please see the details below.
Get all available options for product attribute
Request Method : GET
Request Link Syntax :
<base_url>/rest/V1/products/attributes/<attribute_code>/options
Request Link in your case :
http://magengree/rest/V1/products/attributes/manufacturer/options
Add new option for product attribute
Request Method : POST
Request Link Syntax :
<base_url>/rest/V1/products/attributes/<attribute_code>/options
Request Link in your case :
http://magengree/rest/V1/products/attributes/manufacturer/options
Request Body : JSON(application/json)
{
"option":
{
"label": "Apple",
"value": "214",
"sort_order": 0,
"is_default": true,
"store_labels": [
{
"store_id": 0,
"label": "Apple3"
}
]
}
}
Delete any existing option for product attribute
Request Method : DELETE
Request Link Syntax :
<base_url>/rest/V1/products/attributes/<attribute_code>/options/<option_id>
Request Link in your case :
http://magengree/rest/V1/products/attributes/manufacturer/options/214
Make sure you add Authorization token for all request.
For more information Refer catalogProductAttributeOptionManagementV1 from https://devdocs.magento.com/swagger/
Hope it finds you helpful.