That sounds like heavy residue loading, not just “needs more passes.” If the carpet is sticky and stiff after multiple extraction passes plus an acid rinse, I would treat it as detergent residue that has bonded into the pile or possibly residue plus soil redeposition.

Stop adding more random chemistry
You already tried hot water extraction and an acid rinse. I would not keep stacking products, because that can make the residue problem worse. The SDS also says not to mix it with other chemicals.

Flush, don’t “clean”
Use plain hot water and make your goal residue removal, not soil removal.

Agitate before extraction
Use a counter-rotating brush, groomer, or soft brush to break the residue film before you extract again. If the pile is glued together, plain extraction may be skimming over the top and leaving the worst of it behind.

Do a towel test
Dampen a white towel with warm water and scrub the affected area by hand.

- If it gets foamy/slimy, you still have detergent residue.
- If the carpet stays hard with little transfer, you may be dealing with residue locked into the fiber or possible texture distortion from overwetting/soil suspension.

Set realistic expectations
You may improve the carpet a lot, but it still might not feel completely soft and normal after one cleaning attempt. Some cases need:

- repeat flush extraction after drying
- low-moisture encapsulation after residue removal or, worst case, acceptance that the texture has been permanently altered