Hello Micker,
I don't know how you are checking? Just pasting the url in your browser or what?
The webhook url should be called by transifex - transifex also passes some arrays with data. If you just open the url and don't send the data, then you are going to get those warnings. The way to test it is - either simulate the data that transifex is sending or go to transifex and edit a language -> whenever the language file gets 100% translated transifex is going to send information to the webhooks url.
help.transifex.com/intro/projects.html#webhooks
And also - look at the url -> it has a key -> this key should be kept private! You don't want people just randomly sending data to this url, do you? We check the key with the value in the db and only go further in the script if it matches.
Regards,
Daniel