Your material after filtering still does contain bulk of your gold. That is because resin used in production does not bode well with nitric acid. It swell and bulk up possibly encapsulating tiny bonding wires present inside.
Incinerate all of that. Like completely so only white crumbling dust remain.
Then use mortar and pestle to crush all of it.
Wash with water, keep wash water, it will be slightly acidic.
Treatment of wash water:
Slowly evaporate 80-90% of that wash water and add small amount of AR there and test it with stannous. If there will be gold present then keep it on heat for a while till no reaction can be observed from mud on the bottom, neutralize remaining nitric with sulfamic acid filter and drop gold from a filtered liquid.
Treatment of crushed material:
Use HCl to cover material and add Nitric in small increments like few ml at a time. Do it on a hotplate on a medium heat, stirring from time to time. Stop adding Nitric when no reaction is observed. Neutralize Nitric with sulfamic acid filter and drop gold.
As for your original drop test it with stannous. You most likely did not neutralize nitric if no gold is dropping out of solution. Stannous test will show if it is still in solution. You did classical newbie mistake using insane amounts of acid. 2 liter is way too much you should accomplish all of what you did in just 1/10th of that.
If stannous show gold in solution then keep the solution on medium heat and try to evaporate 75% of it. Heat will assist with eliminating free nitric. Then use a bit of sulfamic acid just to be safe and try to drop gold again. There will not be much of it there as most of your gold will be still in your material as I said before.