Metz has gone out of business and their website is kaput. I have their M-400 flash.
In 2017 they released M400/Fuji firmware v 1.2 with important features (support for HSS)
Unfortunately, my flash is running v 1.1.
If you have this flash and updated its firmware, perhaps you still have the updater around?
I realise it is a longshot....
Thanks,