Activity, but no kreusen?

Not sure if this belongs here or in the Beginner's forum, but here goes:

I made a batch of Oatmeal Stout yesterday, and while a lot of things went wrong with the process, I'm not sure if this is something I should be worried about.

I pitched about 5:00 last night, and when i woke up this morning I was expecting to see a pretty healthy kreusen in the carboy, as has happened with most of the other batches of beer/cider I've made so far. I was surprised to see no kreusen buildup at all, but even more surprised to see the airlock bubbling away. Clearly there's activity - the surface of the beer is almost static-y with tiny bubble activity - but there's no kreusen at all.

So, I'm wondering, what kinds of things can affect kreusen? Is it starch? Sugars? What gives it its structure, that my batch might be lacking?

I've smelled the gases coming out of the lock and it smells fine. The temp is a little colder than what I would normally keep a beer at (down into lager territory, by accident), but not outside the range for this scottish ale yeast.

I'm not worried about it, just trying to understand the chemistry at work here.

I have noticed similar conditions in the past, and the result is a beer that has no head retention. I don't know why it happens or what is going on, but bio-foam helps a lot.

https://www.homebrewtalk.com/f39/beer-head-86911/
This seems like a similar thread. Do you remember the stages to your mashing and what did the grain bill consist of. These things can affect the beer head. Proteins make up the head but many things can destroy it. We have probably all had beers with a terrible head. For some reason when I do a decoction mash my beers have terrible head retention and formation

I expect the thing that really 'broke' my beer was that I wasn't able to do much of a sparge at all to get the residual sugars and proteins. I was brewing-in-a-bag and when I tried moving the bag from one kettle to the other I dropped it. Made quite a mess, and in cleaning up I basically made the rest of the grain unsalvageable. I had to add some top-off water to the carboy to get back close to 5-gallons, so I'm expecting this to be a pretty thin batch, but I was hoping to still have a decent beer in the end.

Guess I'll just have to wait and see what happens!

What yeast? I'm going through the same thing and I used Nottingham. Further searching through the threads revealed many people with the same thing using that yeast

This is Wyeast #1728 - Scottish Ale. Not sure if it's a Nottingham clone or not, though I would guess not.

Aaaaaand now there's no activity, either. This has got to be the weakest beer I've ever made. Going to check the gravity tonight and see if it's really done already, or if something has gone horribly wrong.

give it time. You need at least 4 days before you can panic about initial ferm

Okay! Here I am, four days after pitching. The fermentation has almost completely ceased (the airlock is completely static, and there is only the tiniest of bubbles periodically breaking the surface), and my gravity is stuck at 1.020. The beer still smells fine, doesn't show any obvious infections, and might still be salvageable, but I would rather get the gravity much closer to 1.0 before I bottle.

Any suggestions for how to kick off fermentation again? Would another pack of yeast do the trick?

Amylase enzyme. Start with 1/2 teaspoon and wait a few days, check gravity. Don't overdo it.

Thanks for the tip, Tre9er! I'll give it a shot and report back in a few days...