Connected via MacBook -> USB-C-to-Thunderbolt adapter -> Thunderbolt-to-Firewire adapter ... it still worked until today.

The last months some problems began to approach. After connecting and powering on the interface, the LEDs flickered and I could hear some flappy noise, which got higher and higher in between of seconds, until the artifacts finally disappeared - incompletely. There was still some noise. My usual procedure was to dis- and reconnect the power of the interface. After booting up the second time, it always worked perfect.

Today, the interface stopped playing any sound. The OS is still able to detect and select it as usual. TotalMix even shows the interface playing. When dis- and reconnecting power again, the results differ from time to time. Sometimes, the LEDs lighten up just a bit. Another time, everything keeps dark. Sometimes I hear some noise rising up and disappear. Left and right at a different time. Then everything looks like normal again. In any case, the interface seems to refuse playing back any more sound coming from the computer.

I checked the output of the AC adapter: 12V. No idea, if it still delivers the required 12W, like the label above the interface power input shows.

Any idea how to further check, fix this or what else to do?