It sounds like there is air in the system and it went from into the reservoir to the brake line so it went soft and then back into the reservoir. I used a cheating method to bleed my Formula Oros (same bleed prodecure as Avids) when I had the same problem.
First of all tie the levers back to the bars to let all teh air into the resvoirs. Then, push the pistons back and use something to stop them moving forwards. Now, put just a little bit of brake fluid (2-3ml but it doesn’t really matter if you use a tinny bit more) in the syringe and de-gas it. Undo the bleed port and screw in the syringe. You can then just suck the air out. Also try a couple of pulls on the brake levers to knocks any air bubbles and let them to the top, then suck them out. You can also, after pulling on the syringe, push fluid back in and repeat. Remember to have the syringe upright otherwise all the air you painstaking took out will go straight back in.
Keep doing this until you’re confident that there’s no/next to no air in the system. This is probably the most important step: push fluid back in. This refills the reservoir adn gives you a nice firm lever feel.
It worked perfectly for me, give it a go.