I have researched the tech "Galvanized Steel Machined Parts Processing" (red tech). In this research you unlock "Corrosion Resistant, Load Bearing Large Paneling" (a mouth full). According to the recipe book mod, this item is crafted in a Welder. But the Welder doesn't see the recipe. This blocks me from crafting this particular item, which prevents me from building oil processing and progressing to blue tech.

I did have four oil refineries in my inventory already. So in an earlier session I could build these already. But now I can't build any more of even a single Chemical Plant.
It looks like an update broke this recipe and now I'm stuck in progressing the save.

i just reached blue science and have successfully crafted an oil refinery. welders do have a recipe for [[corrosion resistant, heavy load bearing large paneling]]. it is on the fith row, and is the only recipe in that row (at least at this point in the game).

the tooltip for [[galvanised steel sheet stock]], which is required to make [[corrosion resistant heavy load bearing large paneling]] incorrectly reports that it can be made in a roller. it is in fact made in an electroplater.

i was able to craft an oil refinery and a chemical plant.

the mod was last updated 21 days ago, so i don't think there's been a fix to this issue. is it possible you didn't notice the item you were looking for in the welder's recipe list?

if it helps, here's a handfed blueprint that worked for me:
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the ovens are there to tell you which machines to handfeed, i don't expect you to be running around with ore in your pocket.

I don't have the electroplater, even though the research says I unlocked the item already..

Looking through the changelog, the electroplater is added in the last update. I started my playthrough in the previous version. I guess something broke and the fix is to start a new game.

I've started adding migrations to the updates. For now, just enter /editor mode from the console, and un/re-research the minisembler tech (and, while you're there, the rest of the tech's I added :) ). To research it instantly from /editor, shift-click the "Start Research" button. :)