Adding or removing a mod has the possibility to remove your ability to make "uncommon" items, at least until quality modules are researched. I would maybe add a research to the start of the game - unlocked by mining 1 iron ore - that researches "uncommon" quality.

I mention this, because I lost my uncommon. I fixed it with the following to changes:

[data.lua]
require("prototypes.technology")

[prototypes\technology.lua]
data:extend
({
{
type = "technology",
name = "quality-uncommon",
icon = "quality/graphics/technology/quality-module-1.png",
icon_size = 256,
effects =
{
{
type = "unlock-quality",
quality = "uncommon"
},
},
research_trigger =
{
type = "craft-item",
item = "iron-plate",
count = 1
},
upgrade = true
}
})

[locale\en\locale.cfg]
[mod-setting-name]
base-quality=Base quality

[mod-setting-description]
base-quality=Percentage points of quality that will be given to every machine (i.e. 10 = 10% base quality).

[technology-name]
quality-uncommon=Uncommon Quality

Works for me, anyway.

Eh, I was a little hasty. Edited the above post, twice. I'm satisfied with it now.