Victoria II´s economy works like it is designed. The here described problem (like already said in the thread) is that your pops can simply not afford your goods. The UI will only show you that they need for example 14t of liquer (beverages in your mod), but the UI will not show you that your pops can only afford f.e. 7t. of liquer. Most of the "I dont understand Victorias economy" problems are that the UI is doing an very suboptimal work in showing us what is really happening.
You could try to lower the taxes on your poor pops and also activate social reforms like minimum wages to improve the money your poor pops have. Also you should have at least some capitalists in every state where you have factories ( support up to 0.2%, that is enough for the start, they will raise their number then from alone). Capitalists gets uneblievable rich from owning factories and this provides a good chunk of healthy demand in your own country and boosts your economy. I call it "healthy demand" because capitalists can actually afford to buy nearly all the things they demand (which your poor pops most of the time can not, and capitalists, even when on lower numbers demand a lot more goods "per 1 pop". Also you will indirectly loose money (possible tax and capitalists invest money) if the state has absolute no capitalists, because only they can get the sureplus money a factory is making (workers only get a fixed % as wage, and every sureplus money is either lost or goes to the capitalists pocket.
A huge design problem in Victoria IIs economy is that there´s only one world market which means only one price world wide for the products. This can and will lead to situations where your economy is providing f.e. 50t of liquer, your pops need 80t of liquer, but they can afford only 20t of liquer, because every other country on the world is producing too less liquer, so that the price on liquer is raising since years and your own pops can not afford the liquer produced in your own country, although you have tons of it.
If we ever get Victoria III it must have a local market price, where if you produce a lot of something, the price of this good is going down in your own country, although the price could be raising on the world market, because the other countries are not producing enough. Also an option to simply dictate a price in your own country would be nice, even more nice for communist countries, but also capitalist countries did this from time to time.
Even better would be to have the prices be calculated per factory instead of per market or country. Then we could have f.e. a factory in Silesia producing steal a lot cheaper then a factory in Hanover, because theres no iron rgo in Hanover, which mean higher transportation costs for the factory in Hanover. This could lead to realistic economy situations where factories will be build from capitalists exactly where the capitalists can make the most money out of it.