In case of anisocoria when 1% pilocarpine is instilled into the eye with abnormally dilated pupil, pupil remains dilated. Cause of anisocoria may be-
Anisocoria refers to difference between the size of two pupils. In the question, anisocoria is due to abnormally dilated pupil (Has been mentioned in question).
Pilocarpine is installed into the eye with dilated pupil and there is no constriction. (pupil remains dilated).
Pilocarpine is a direct muscarinic agonist and cause pupillary constriction.
Response to pilocarpine is as follows:

Pupil will constrict with 1% pilocarpine in 3rd nerve palsy, anxiety state pupil, sympathomimetic drug use.
Adies pupil constricts even with low dose (0.125%) as there is denerration hypersensitivity in Adies pupil.
A pharmacological dilated pupil will not constrict after pilocarpile instillation. Other conditions where dilated pupil will not constrict are fixed pupil (iritis), and traumatic mydriasis.

Mydriatic drug effect (Pharmacological block).
Fixed pupil (iritis).
Traumatic mydriasis.
3rd Cranial nerve palsy.
Anxiety state pupil.
Sympathomimetic drug induced dilatation.
Adies pupil
Pharmacological blockage
Uncal herniation
Diabetic III cranial nerve palsy