Sure, I need to delete it but i get this error:
I mean delete the user in AD. You can't delete AD users in ownCloud user management tab
Ah! No, I can't delete the user in AD directory. This is an important user with mail. This is not an option.
So your goal is simply to allow this AD user to log in into owncloud? You don't care about the data, right?
I don't care about data I only want this user log in to owncloud, being able to upload files with his new password.
Okay, you would have to delete the entries of this user by hand in every table his UUID is in.
How versed are you in mysql? 
You would have to do a mysql query. Log in to the database, and do something like this:
Delete from where =25A7B9BE-XXXX-XXXX-XXXX-424445615463;
Then when you are done with that, you have to delete the home folder of this user
Then the user can login. I would also remove him from the users that are synchronized in to owncloud. and when you are done cleaning up, include him again.
Which table I have to delete the user?
In oc_users I don't see the user because is connected via LDAP. I don't know where he is.
You would have to look in all the 46 tables for his uid, this long number, not only in oc_users
Are you sure it will work?
It's dirty as it gets, but if you remove all the user IDs from the database, it should work. I don't know any other way to do this.
@mago Which version of ownCloud are you using? Please can you look for the user in oc_ldap_user_mapping table
We're using 9.1.4 (stable).
There was a bug regarding this. I think it was fixed in 9.1.6. You might want to update to 9.1.7 and retry.
I’m having the same problem again with other user, ¿is it fixed?
have you upgraded yet?
Yes, we’re in version 10.0.1 and still having these problems with LDAP users.
The user forgot his password and we removed his user account.
He tried to log in again and owncloud still saying he has problem with the password.
Have you checked if he is not blocked in LDAP?
If you are using AD as the LDAP there is a function that blocks users who typed in their password wrong a few times.
Yes, we’ve checked it.
He is using his user in other tools and he can log in into owncloud but pops up the advice telling he need to put his old password to encrypt the files again, but he doesn’t remember the old password.
Oh, I did not realize you were using encryption. Master key or user key?