Quail absolutely love not lay

[007Sean]

I had the same issue in past and it was because I had too many roos with the hens. As soon as I removed the roos, I had eggs within 10 days. Personally, I'd pull all roos until they started laying. Similarly, consider if anything else may be stressing them - most commonly predators that approach the quail during day or night. If separated, roos won't be very nice to each other so you'll need to keep an eye on them - although I've never experienced more than a few head/back feathers missing when I caged roos together.
Also look at feed. I'm assuming your feed is layer feed so they are getting enough calcium. If you are on a meat bird 'grower' feed, it needs to be switched to a layer crumble or it won't have calcium in it to form eggs. Switch to a standard brand 'layer' crumble - not any of the 'designer' feeds - no mixed grain feeds (known to have unpredictable results), feed mill blends (less likely to have issues, but might as well rule it out), or 'vegetarian' feeds (known to be cause of laying issues). It can be a game feed, turkey feed, or chicken crumble feed - as long as it is the 'layer' version and a crumble where they can't pick and choose what parts they eat. Pull all treats and scratch until they are laying.
I can't see how you are feeding them in photos, but free feed them - they should have feed available at all times. If you are trying to put out what they 'should' eat to limit waste, consider if they toss half on ground, they are under-nourished.
Again I only suggesting you wait until after they are laying to try to limit waste because that is the issue you are experiencing. I took away supplemental light too early in spring once and mine stopped laying - I immediately knew the cause.
The last items I can think of are temperature and genetics. I've only grown quail in a temp controlled environment so I can't speak to that.
Personally, I wouldn't consider buying new quail for genetics. Your lines can be adjusted by you with selective breeding - to hasten, just get a couple of birds with traits you want. Once I had eggs being laid, the first hens to lay never mattered to me since I had more than I could use. If you want quick laying hens, separate the first to begin laying (although I suspect yours will all start within days of each other) & hatch eggs from offspring of hens that lay earliest. No matter where you source your quail, you have to selectively breed to keep any trait.
I never saw a difference that mattered on how many eggs a hen laid per year - all of mine laid 5 or more eggs weekly. If you want quail that get larger faster, only hatch from eggs from those hens & roos.
I don't eat much quail so size isn't really my selection criteria - I want the largest eggs & really from the smallest birds (for higher conversion rate). My largest birds tend to produce the largest eggs. I haven't been successful getting small birds with large eggs with such a small flock. I'm just getting larger quail & eggs.
Best of luck!

My largest birds tend to produce the largest eggs. I haven't been successful getting small birds with large eggs with such a small flock.
Well, duh!!!! You can not expect a small bird to lay a larger than normal egg. Breeding for that trait (large eggs from small birds) will only result in the hens having reproductive issues; peritonitis, egg drop syndrome, and/or egg binding....shortening the life span of the birds.

 

[FatherFalcon]

I have jumbo coturnix quail that absolutely refuse to lay. They are over 4 months old. Have 21% protein, 16 hrs of light, 1/9 male to female ratio, plenty of space, constant clean water source. I’m at a loss what to do. Should I just get new stock? So frustrating.

After Reading the Threads... Yes to a majority of the suggestions...
Ideally... in my mind's eye

In small spaces; Free roam/greenhouse/etc.......
Aviary/ Runs/ Pens/ Hutch/Nesting box; safe place to lay an egg
area coverage ( a dark spot to hide)
Rollout cage: forced conditions and no choice to lay in place

Temperature/Humidity ... I find that quails thrive in warm heat.....
68-74 degrees seems perfect... don't want them sweating...
but enough to keep them dry
35-40% humidity so the air is moist enough to keep their lungs healthy
but desiccant enough to dry the poop (environment variability)
Food and Water; availability, proximity, nutrient value
(purpose layer or meat/broiler)
water temp* ? i know cold water sucks and they drink it less often. ?
Health/ Energy; do they have bubble guts, hard poop,
genital blockage (butt feather dreads...)
As for the light.. yes 16-18+ hours a day
(or......... PERPETUAL DAY!!!!!! Evil LAugh)
I agree that birds want the sun to do most of the work
type of light and brightness
does the light have a refractive pattern?
lights might have a type of strobe or flicker?
brightness of the lights hmmm... 5500k-6500k
which would you think the birds want?
blaring white bright squinty eyes blinding glow or
smooth operator warm afternoon mimosa on the beach orange soft glow...?

Sing to them...