Google Sheets API via POST Webhook

Does anyone know how to use the Google Sheets API with Hologram? I’m trying to write to a 100% public Google Sheet, but for some reason, I have to authenticate.

I have read the Google Sheets APIv4 docs and I have tried attaching my API key both at the end of the API URL as ?key=keygoeshere and as a basic authentication with the username Bearer and the password being the API key, as well as both simultaneously. Each time I get the error:
image

Here’s the full webhook. Any information is greatly appreciated!
Full URL: https://sheets.googleapis.com/v4/spreadsheets/SHEETID/values/Sheet1!A1:F1:append?key=APIKEY
Payload: {"range":"Sheet1!A1:F1","majorDimension":"ROWS","values":[["<<received>>",</received>"<<decdata.Lat>>",</decdata.Lat>"<<decdata.Long>>",</decdata.Long>"<<decdata.Alt>>",</decdata.Alt>"<<decdata.Head>>",</decdata.Head>"<<decdata.Sat>>"</decdata.Sat>]]}