How to debug a light fixture that is no longer working
It looks like you have two circuits, black and blue wires and a white neutral, coming out of the center conduit in the old fixture box. The black wire is wire nutted to a group and one of them goes up the left conduit with a neutral to the switch box to feed the GFCI outlet. In that same conduit is the always hot blue and what will be the switched hot red when hooked up to a switch. The switched hot in the old fixture box leaves in the lower left along with a neutral to the new fixture box. Check your main panel for two breakers that energize the old fixture box. They may not have handle ties on them