Trying to figure out why no sound with coax using iFi spdif iPurifier

How could a coax run from Oppo to DS dac work fine, but not with an iFi SPDIF iPurifier inserted inline? That’s the predicament I’m trying to figure out. I have a coax run from an Oppo 203 to a DS dac in which I’ve used an iFi spdif iPurifier for the past year. It goes in series on the destination end and uses a 5v power supply, in this case a Paul Hynes SR4 (set to 5v). The other day, after changing some cords around, I reconnected the power and got no sound. I then tried different 5v power supplies and cables, including iFi’s supplied ones, and tried both wall and P15 outlets, but no luck. Also got no sound using the toslink port. However, a coax run w/o the iFi sounds fine. To check if the unit is the problem, I got ahold of another (used) one and got the same result with it. A new replacement from iFi is still several days away.

The tests I’ve mentioned would seem to leave only the input to the iPurifier or the connection from it to the DS as possible culprits. I put another cable (and thus connector) between the coax and the DS (no iFi) and the sound was fine, but when the iFi is reinserted, no sound. Then looking at the output side, I pulled out a multimeter, set it to the 200 mV scale and played a video. With one lead against the iFi’s outer connector sleeve and the other on its tip, there was a varying voltage reading, as I assume would be the case with something playing (but I didn’t get any readings with the coax alone, and am not sure why). I assume that means the iFi’s output to the dac is getting through to there.

Any ideas what the problem could be or what I should be looking for? I’m not sure how it would be, but am wondering if there’s something inside the dac’s port that is not getting along with the iFi now for some reason, but is ok with the coax alone. The iFi’s connector did break off in that coax port early this year, but PS Audio replaced the port and I got another (new) iPurifier. This one has worked w/o problem since then…until the other day. Here are some stock photos to give a picture of the thing. Thanks,