405 error, "method not allowed" when I try to update API items

I am writing a Python script to use a spreadsheet to add items to an Omeka S API. I’m following the instructions here and using the API client described: Omeka S API client | omeka_s_tools. The following error happens when I try to update an item:

requests.exceptions.HTTPError: 405 Client Error: Method Not Allowed for url: http://nnn.nnn.edu/omeka-s/api/items/2422?key_identity=xxxxxxxxxx&key_credential=xxxxxxxxxx

The server administration has allowed PUT requests on the server. It appears to me the request is being structured correctly according to Omeka S’s REST API documentation. When I look at the API endpoint above I see the item with all its data. Although there may be issues with the code I’m using to update the fields, I get the same error if I simply retrieve an item from the API and send it back. I do not get this error if I add new items to the API

You’re sure the host is allowing PUTs?

We don’t return 405 errors in very many situations, so I’m wondering if this is happening at a level “above” Omeka.