discord has changed the default endpoint url to discordapp.com and broken dhooks parsing
discord seems to now be using discordapp.com instead of discord.com in their webhook urls (discord.com still works for now, so you can just remove 'app' from the url) and dhooks doesn't detect the discordapp.com variants as valid webhooks. idk if this module is still supported but if not then maybe it will help someone else running into the same issue
https://github.com/kyb3r/dhooks/blob/cdd5f3f3bc109cbbc06f16a1cd9d39ed9d75a94e/dhooks/client.py#L120 https://github.com/kyb3r/dhooks/blob/cdd5f3f3bc109cbbc06f16a1cd9d39ed9d75a94e/dhooks/client.py#L478
these seem to be the pertinent lines
EDIT: i looked into some older issues and it seems like I somehow managed to get an outdated version of the module through pip install without the most recent commits which addressed this. it also sounds like discordapp.com is the old endpoint but discord still gave me that url through the built-in "copy webhook" button today.
You should probably look at lovvskillz/python-discord-webhook instead of using kyb3r/dhooks.
But it looks like lovvskillz/python-discord-webhook also has problems https://github.com/lovvskillz/python-discord-webhook/issues/159