I've never heard of or seen such a thing, but I'd be extremely suspicious of cloudy mineral spirits. There are some new "VOC compliant" versions around, but I wouldn't trust them for anything other than washing out brushes (if that) without extensive testing. I'm assuming that you're using oil-based poly.

Poly needs moisture in the air to cure. It's lacquer and shellac that do poorly in very damp conditions. Moving air also helps.

I think I recall seeing some white low-voc paint thinner on a job once, but I avoided it.

Hopefully the two different poly's were from the same line of the same brand. If they were different brands, that's a no-no.

I once used a 'new' can of floor poly--- it would not dry either---turns out that 'new' can(bought from a home improvement store) was three years over the Use By date.

Like Casey wrote, mixing brands is a no-no as is mixing batch amounts or widely varying Use By dates.

Thanks. I'll check the dates. Both cans are by the same manufacturer.

I really wish now I'd done a test first. Until recently, I'd always used turpentine when thinning poly. As an artist, I'd always used turpentine to dilute oil paint. And thinner to clean my brushes. But then I read on some forum that using turpentine was unnecessary, that mineral spirits was good enough. Otherwise I would have reached for the can or turpentine when mixing my finish.

I will let it dry a few days, before deciding if I need to remove it. The walnut table top will be ok. That's drier than the 2 oak pieces. Don't know why.

Finish that fail's to dry is one of the most disappointing problems one can have. If it eventually dry's it will likly not be durable so I would remove it now rather than later. Right or wrong,what I've done is let surface dry a few extra days after cleaning before staining/refinishing.