Is the repentance of one who stole in his youth and then repented accepted, given that he now suffers from obsessive-compulsive disorder (OCD) telling him that his repentance is not accepted because he did not return the stolen items to their owners, and it is difficult for him to return them because he does not know them or the quantity stolen?

Allah Almighty is gentle with His servants and merciful towards them. He, glory be to Him, does not burden a soul beyond its capacity. It is obligatory upon you to deliver the rights to their rightful owners whom you know, and it is not necessary to inform them of what transpired. The objective is that the right is returned to them by any means. As for the rights whose owners you are unable to identify, or you are unable to reach them to return their rights, it suffices for you to give charity on their behalf equivalent to the amount of those rights.