What kind of tasks that can’t be done are you seeing?
There’s a good post explaining the daily tasks here.
The first task on the list, which is usually the one that’s not doable for me (level up a troop when all my troops are max level for example), resets every day as is.
The other three tasks should usually be doable, they’re the win x games with x team ones or win x battles, earn x trophies. I’ve always found those doable, but that’s coming from someone with all troops, so it might be different when you have gaps in your collection.