AirPods Max Not Working

My first generation AirPods Max all of a sudden won't connect to any of my Apple devices, all of which are running most up-to-date software.

Restarting AirPods Max--by holding hold the digital crown and the noise control button at the same time until the status light next to the charging port flashes amber--doesn't work.

Nor does resetting them--by holding the digital crown and the noise control button at the same time until the status light next to the charging port flashes amber and then white--fix the problem. In fact, when I press and hold both the digital crown and the noise control button, the amber light flashes on three times. I am never afforded the opportunity to set them, which used to happen automatically. So I'm stuck.

Any suggestions aside from literally taking them in for repair, to be told that I need to spend hundreds more Euros on yet another set of Apple headphones that have randomly stopped working?

And yes they are fully-charged; and yes I can connect other bluetooth devices to my aforementioned Apple products.

[Edited by Moderator]