For a few years we've been using Travelite 750 strobes with a 60D and an 80D by setting on-camera flash to 1/128 power -- enough to trigger the strobes with effecting the shot. Camera set to ISO 100 and 1/100-sec shutter. However, the same setup with the 77D doesn't work -- although the on-camera flash triggers the strobe, the image captured in the camera does not catch the strobe flash. As if the shutter is operating after the strobe has finished its flash. Changing shutter sync to 2nd curtain has no effect.