The water is 80 degrees.
Try bumping up the temperature a bit. Spawning in the wild takes place when the weather is warmest, and there are plenty of food sources available.
I have a 20 gallon tank.
You should either divide the 20 gallon for spawning, or use a smaller tank. In my experience, it's easy for the male to get side-tracked in a larger tank. A lot of breeders are starting to use clear plastic tubs from Walmart- they're cheap and filled to 5 inches or so, the male is consistently in the female's vicinity.
Ive introduced the male n female plenty of times but not freeley in a jar or something. Leave them together for an hr or 2. Gave them their time apart. Tryed leaveing them were they could always see eachother all the time.
You should keep them completely separate from one another while conditioning for at least 2 weeks. Conditioning should consist of high quality food, and a variety of it. Clean water is also a must.
The male shows off. Flutters his gills etc.
Does he wag his body in an "S" fashion around her? Does she seem interested or bored?
There is a place he can build it that has no current or anything.
It's a good idea to invest in Indian Almond Leaves. 9 times out of 10 the male will build a nest under the leaf rather than anything else. It also fills the water with beneficial nutrients that induce spawning and help build the fry's immune system against disease.
Feed them freeze dried blood worms at night.
I never recommend feeding freeze dried blood worms. They bloat the stomach and can cause other serious issues. Is this all you've been feeding them through conditioning? If so, you'll have to re-condition, freeze dried bloodworms are not nutritious enough to get the bettas into the spawning condition.
Do u thinlk its the male/? Should i try new fish?
Follow this advice, as well as the advice of other breeders here, and try it again. If you have everything perfected down to a T, it could be that your male is a procrastinator. I've had males that refuse to build a nest until they begin the actual spawning. If they never do spawn, you could have a personality conflict. Sometimes just like people, bettas just don't click. It's important to have 2 males and 2 females of the same finnage/color you are going for in case a personality conflict arises. This way you can have 4 different combinations.