Most electronic transformers employ self oscillating methods which rely on the load current for oscillation, hence the characteristic minimum load requirements. Since LED lamps consumes much less power (current) than it’s halogen counterparts, it could be that the lamp current is too little to initiate the transformer oscillation and hence turn on. This is especially a possibility if the supply voltage is relatively low and with a low total load on the dimmer.
Follow manufacturers recommendations for transformer compatibility and minimum number of MR16 LED lamps per transformer. If this is according to specifications, activate the MR16 LED compatibility mode of the SDIM-T-LED.