I gave the Forma a static ip address (one I know has never been used) and... it works!
Very strange. There is no configuration for the ip address it had, but I guess somehow some other device had it and... well..
Thanks Peter!
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Ok, I'm a moron... I probably tested something some years ago with a device that got that ip-address... because now I found a setting in the router blocking all ports for that address... arggh....
Mods, please feel free to remove this thread...