Help me germinate some roselle hibiscus

I'm at the end of my rope here. I've read everything I could find online and tried a few different things but my Roselle seeds still don't germinate. Anybody have hints? Maybe I need to buy a new packet of seeds? The goal is to turn this into a side hustle so I can sell a few plants a week. Here's what I tried, for a total of about one month now--

- Put the seeds in potting soil in an indoor greenhouse
- Put a heat mat under it and consistently kept the temp between 75-86F (~26.5-30C)
- Watered at least once a day to keep the soil moist
- Gave up on the potting soil, tried coconut husk "starting soil" instead
- Tried turning the grow light on and off. I don't think it does anything except add more heat, which I don't really need
- Tried nicking the seeds and soaking them overnight
- Tried folding the seeds in paper towel and spraying it twice a day. I think the paper towel dries out too fast

Did you soak the seeds?  If not, start over with seeds soaked overnight.

Then put them in a moist paper towel in a plastic bag and seal.  Check daily to make sure the paper towel is moist.

If after a two weeks nothing has happened, try a new seed packet.

I feel for you Andy! Sometimes a plant you want seems impossible to germinate. I get the impression that these are seeds you bought? I have to wonder if they are good seeds though. Have you asked the vendor for advice?

Andy!! I was just telling my mother about my own saga germinating these little stinkers. I live in zone 9b, and its supposed to be a hot summer, so I figured this would be a good year for them. In my experience they do well in 10+, but i'm an optimist.
I special ordered the seeds, tried once normally (soaked seeds, mix that worked for everything else). Nothing.
Tried again, nicked and soaked seeds, nothing. After 6 weeks of watering I started a new flat of something else and moved that flat to a hotter part of the yard and kept watering, and lo and behold 3 of the dozen i planted came up. It was HOT, like 35C+.
I transplanted the three seedlings. One fell victim to the feral cat that likes to poop/scratch in my garden, dirty rat. Another one was doing fine until this week, when it seemed to decide it didn't like living and decided to wilt away. Number 3 is looking okay, but I don't see myself getting the big old harvest I expected. We shall see.

Roselle has to be one of the hardest things I still stupidly insist on growing. But it wants hot hot hot.

Hi, roselle is native to where I live, and I can confirm that sometimes they just won't germinate. Usually that means they're too young. Keep  them till next year and they will probably sprout nicely.

It is not clear to me whether it's dormancy or heat layering that makes them sprout well. Might be both, because some people around here will plant young seeds after pouring boiling water over them. Give it a try!

I had accidental good luck with germination last year.
In a 'Going to Seed' packet there was a mix of seeds that I scattered and watched for them to come up.  In the end the two I couldn't ID without help were the roselle plants.

I planted the seeds in the rain, maybe lightly mulched and didn't pay any attention until they were more than a foot tall.

After reading this thread I doubt I could duplicate my luck!

our season was not long enough to mature seed.

https://permies.com/t/361235/hibiscus-Roselle

I lived in 8b/9a for over three decades. My experience with the hibiscus family (roselle - we called them rosella -  and okra are in this category) is that they do best germinating outdoors, in the ground (not as transplants) and for me that was usually May at the earliest. Sometimes June and they would produce until killed by a hard freeze or we overwintered them indoors and they kept going the next year.