First check whether a store is full
The number one reason production stops is not the factory, it is capacity. When one product's store fills, that link halts; once it halts the link before it has nowhere to put its output, and the chain locks upwards. The result looks like "harvesting has stopped" or "no fabric is being made", but the cause is elsewhere.
Stock counters in the HUD flash red when they fill. The game also raises a problem card on the left naming the jammed link and what to build. If that card is up, do not look anywhere else: build a silo or a warehouse.
Capacity is not increased by hand. Total capacity is derived from the factory level, the workshop level and the silos and warehouses you have built. Building storage, and upgrading the storage you already have, matters as much as any production upgrade.
Factory and workshop levels
The factory turns cotton into yarn and yarn into fabric; the workshop turns fabric into garments, two fabric to one garment. Both levels raise their rate.
The important detail is that each level adds to the rate rather than multiplying it, so the percentage a level adds shrinks as the level climbs. Going from 5 to 6 is a large step. Going from 40 to 41 is a small one. This is why the upgrade button shows a "now → next" value: you can see what you are buying before you pay for it.
The gin is the line's real multiplier
The gin is the strongest lever on the production line, because it does two things at once: it speeds production up and it lowers the unit cost. When a long-running player says they cannot increase fabric output, the usual reason is that their gin has reached its ceiling.
That ceiling is no longer a fixed number, it grows along with your level, so a heavily upgraded gin is not wasted money. There is still a ceiling though: you cannot solve everything by upgrading one building forever, and past a point the money belongs somewhere else.
Line modernisation
A repeatable upgrade that unlocks after level 8. Each purchase multiplies factory and workshop speed, and there is no limit on how many you buy; only the price grows.
This is the real answer to "there is nothing left to spend on" in the late game. One caution: modernisation raises production, and production raises energy demand. Buy several in a row without looking at the power side and you can drop into a brownout that slows the line back down.
The order to upgrade in
- Capacity. If a store is sitting full, no other upgrade means anything.
- Supply. If the factory is faster than the harvest, grow the field and collection side first. A starving factory runs empty no matter how fast it is.
- Gin and canteen. Speed and unit cost together.
- Factory and workshop level.
- Modernisation, once the cash pool is large.
"I keep upgrading but the current value does not move"
Some facility bonuses saturate at a certain point. The panel says so by printing maximum and refusing further upgrades. If the panel does not say maximum and the number still refuses to move, that is a bug and we want to hear about it: write to us. Exactly two facilities behaved that way in the past, and both were fixed from a player report.