Paste/sync/denoise doesn't work again!

For a while now whenever I try to sync/paste or use denoise it will work a few times after ive started up lightroom. But after a few times it just doesnt work anymore.. Only thing that will "fix" it is restarting Lightroom and then it will work. It is reeeeally slowing down my editing. Anyone else have this problem and maybe even the real fix?