I just encountered this message too. I handplaced a
ton of grass sprites for a meadow area, then tried to select them all (through the sprite list on the left of the screen). It took about a second for all the sprites to show a blue box around them, and then that message appeared: "A required resource was unavailable." No matter how many times I clicked the confirmation box, it wouldn't go away. Had to ctrl+alt+del to close Construct.
Luckily I had saved before trying to select them all, so I don't need to do it all again! But I want to select them all so that I can add a sine behaviour to them, making them sway. If I can't select them all, then I may well have to delete them all and start again anyway...
Anyone know if this is an issue that can be solved? I'd rather save myself half an hour of repetitive work if I can