how to get it to work with Mailgun? It doesn't work (anymore)

I swear I tested this about 9 months ago and I was able to receive an email through laravel-mailbox. Today I tried it again and this time I am getting `Invalid Mailgun signature or timestamp., Url:https://api.redacted.com/laravel-mailbox/mailgun/mime` errors

I'm using the `HTTP webhook signing key` which has to be the right one

I've gone inside the Mailgun Routes and set the `forwarding` to forward a copy to `https://api.redacted.com/laravel-mailbox/mailgun/mime`

I've followed the rest of the setup guide and I can't figure out what I'm doing wrong!

Can someone please help me out.. thanks!