Sometimes it can take a few attempts before something new is recognised as food.
Previously I had grown algae on wood and rocks in few small tanks on a sunny windowsill, so a lot of my gang were used to recognising "green stuff coating some decor" as edible. I introduced the Repashy foods by spreading it on rocks or wood while runny, and then letting it cool. Pop that in the tank, stand back, watch them ignore it for up to an hour before one of the brave fish gives it a go, then let the chaos commence.
There is a knack to getting the food onto wood. I use driftwood which has to be soaked so it will sink, but the food doesn't stick to wet wood, so it needs to be wiped, then I use a hairdryer to partially dry one side of wood, before spreading on the food and letting it cool. If the food doesn't stick it just floats off in pieces when it goes into the tank. Sometimes it's easier to use slightly rough rocks.
I don't know if my gang are all just a bunch of piggies when it comes to food, or if it's a safety in numbers thing, or they're just used to getting food in various guises, but most of them will give anything a go. It is impossible to put algae wafers in any tank without the mid-water swimmers nibbling at them as they sink, and when they reach the floor, and that's if an amano shrimp doesn't pick the wafer up and run off with it (even the big wafers), before the plecs, gobies, loaches & corys even get to them. Last night I watched in fascination as my largest/oldest penguin tetra caught a mini wafer mid-water and swam around with it in her mouth all evening, occasionally spitting it out to chew a mouthful, then catching it again & continuing until the wafer was gone. I've never seen that before, and I promise I put flake in for them just before the wafers for the corys , BN & shrimp.
Certainly in the river tank I've used soilent green, bottom scratcher and morning wood, sometimes mixed depending on how much of each I have. Every single inhabitant in that tank will eat any/all of them off the wood. In the South American tanks the BNs are a bit shy, but as soon as the lights are dimmed they are onto the repashy, sometimes having to chase the tetras off to even be able to get to it.

Give your gang some time, and try feeding the food to them several times, if a few different ways. If they are used to specific food/wafers, try sticking some on to the repashy food to encourage them to try it.
Let us know how you get on.