if the basestation is amber (yellow) then the basestation cannot see the tau.
(it will usually go to green, even without being connected to a computer)
so sounds like a hardware issue…
it could be as simple as a bad cable, or something wrong at the tau or basestation.
(id guess the cable is the most likely to fail)
quite a while back, I had an issue with my Alpha become a bit ‘picky’ about the cable being plugged in.
i’d need to unplug it/wiggle it about a bit…and then it would start working.
Eigenlabs were great, I sent it to them, they fixed and returned it (very quickly), and its been perfect ever since. (“luckily”, in my case, I had a spare instrument cable - so I knew it wasn’t the cable)
if you are confident/electrically minded - I guess you could open the cable, and basestation to check the connections there - but you cannot open the Eigenharp.
IF the Eigenharp is opened (for servicing etc) , the keys needs to be recalibrated with a special rig which only Eigenlabs have - so its not user serviceable.
so if you suspect the Tau is at fault, then you should contact John @ Eigenlabs