and this no longer works?
... don't take this with a high level authority but while i2cdetect is expected to find all the devices on the i2c bus, I think it can depend on a number of factors whether a response is received or not.
I guess what I'm getting at is that regardless of the output it is worth probing via your program and see if the device respond.
If you have another Pi available (I believe you have?) then it is also worth popping the same SD card in it, and try there. This would allow you to assess, however unlikely, whether there might be a hardware issue with the Pi GPIO.