I have a Canon M3 with Godox X1T-C and TT350-C. It seems the two Godox units are working with each other but my Canon M3 isn't. When I press the test button on the X1T, the TT350C flashes. It even flashes when I mount the trigger on camera. I checked online and the trigger is listed as compatible with my camera.
Please add firmware versions of the 2 devices and clarify what exactly does not work. I guess that the flash fires when attaching the transmitter, but not on taking a photo.– Kai MatternFeb 16 at 10:07
When you say "It even flashes when I mount trigger on camera" do you mean it fires when you slide the trigger onto the hot shoe? (Hint: always turn flash/transmitter off when sliding on/off hot shoe. Failing to turn the flash/transmitter off can damage it.) Or do you mean the test button on the transmitter works even when the flash is attached to a powered up camera?– Michael CFeb 16 at 23:27
If the transmitter already works with the flash, then the usual stuff seems to be ok. The flash may accidentally fire when putting the transmitter on, as the pin for firing my be shorted when sliding it into the socket.
Note that the X1T-C transmitter needs firmware V22 to work with the M3. Current version is V27 from 2019-06-18.
Also the TT350C needs v1.5 for M3/M5/M6 compatibility.
Please make sure both devices are patched up to current firmware levels. Some more details on that: How do I tell if my Godox trigger or flash needs a firmware update?