Constant Current LED

Did you try out all possible combinations of the dimming settings (e.g. leading vs. trailing edge, autodetect yes/no, running calibration) of the Shelly Dimmer 2?

I hope you are using a real LED "driver" and not some (potentially old or reused) "transformer"? Exact make/model information and detailed technical specs of the new LED driver ("transformer") would be helpful.

I assume the new LED driver is also a constant current (CC) driver with 350 mA? Otherwise this is not expected to work. Especially constant voltage (CV) drivers will not work for your scenario.

How many of these 3W-350mA-LEDs do you have connected to the new driver? Apart from the current (of 350mA), also the voltage and wattage of the driver needs to match with the connected load; and the load depends on the amount of these LEDs you have connected.

In addition, the new LED driver needs to support leading edge ("Phasenanschnitt") or trailing edge ("Phasenabschnitt") dimming control. Some LED drivers will be dimmable (and correctly state so on the device), but the dimming control happens over other means (e.g. 1-10V dimming control, resistor dimming control, DALI dimming control, etc.). These dimming control methods are not Shelly compatible.

And last but not least: LED dimming depends on a lot of technical factors and values which need to match each other – and even if theoretically everything matches there will unfortunately be some cases, where it still doesn't work due to technical limitations.

The LEDs you have are 350mA (= 0.35A, current I) and 3W (power P) LEDs. One can calculate the voltage U for each LED using the formula P=U*I, which solved for U gives U=P/I. In your case U=3W/0.35A=8.57V.

You are connecting 3 LEDs in series, so the voltage drop is 3*8.57V = 25.71V for the 3 LEDs connected in series.

The driver you have has a rated voltage range of 60-85V. Thus, unfortunately, the driver cannot provide the correct voltage of 25.71V for your 3 LEDs.

If you would put 8 or 9 of these LEDs in series, they would drop 8*8.57V=68.56V or 9*8.57V=77.13V which is within the rated voltage range of your driver. While slightly outside the rated voltage range, it is quite possible that it will also work with 7 LEDs (=7*8.57V=59.99V) or with 10 LEDs(=10*8.57V=85.7V).

So if you actually have between 7 to 10 LEDs (and you connected „just 3“ of them for your first test), i suggest to connect all your LEDs in series and try again.

Otherwise you would need to find another 350mA driver that has a voltage range that matches the voltage required for the amount of LEDs you want to run off that driver. For this you calculate the required voltage by multiplying the number of LEDs with 8.57V. The resulting combined voltage (for all LEDs) needs to be within the voltage range of the driver.

The driver you have does seem to support the right dimming type for Shelly (trailing or leading edge dimming), so with 7 to 10 LEDs, dimming should also work. The original drivers (and also your new driver) don‘t look anything like DALI dimmers, so that is not the issue.

Oh, and unfortunately it is also possible the LEDs got damaged during your test due to the overvoltage. So i‘d first test them with the original drivers to make sure they are still OK.