Joomla 3.9.3
jDownloads 3.2.63
PHP 5.5.20
MySQL 5.6.21
site is not localhost

It seems to be impossible to modify permissions for a single download. Trying to change the permission for any user group the spinner image keeps rotating and the change is not applied.

The Javascript console shows an error in /media/system/js/permissions.js: document.getElementById(jform_title) is null.

The error corresponds to line 47 in the uncompressed version of the Javascript file, the one starting with "title = " in the branch

   else if (extension == false && view != false){
      asset = option + '.' + view + '.' + getUrlParam('id');
      title = document.getElementById('jform_title').value;
   }

I think the problem to be the one addressed in the source of admin/views/helloworld/tmpl/edit.php in the page https://docs.joomla.org/J3.x:Developing_an_MVC_Component/Adding_ACL/en .
The core javascript code for initiating the Ajax request looks for a field with id="jform_title" and sets its value as the 'title' parameter to send in the Ajax request. In this case the field could be
jform_file_title.

[gelöscht durch Administrator]

HiPermissions cascade down in two ways.  One is through the Categories to the Download, the other is through the User Groups.  The permissions are handled by Joomla! - jD just calls the relevant routines.  I should also mention that if you have a Deny anywhere it can have far reaching effects!!!  So giving permissions to a single Download can be 'interesting'.
Please excuse if I have misunderstood as you may be saying it takes a long time.  That could be down to your server timing out.

Because this is essentially a Joomla! issue to help further we would need Super Admin access to your site.  If you would like us to look please send me a PM via the whitish square with a tail near my name.
You could also use the see permissions graphically facility in Joomla!http://www.jdownloads.net/documentations/item/show-permissions-graphically-an-overviewColin

Hi

I believe I understand how permissions cascade in jDownloads and I concur that this is essentially a Joomla! issue.

It is not a timeout: when you change the value of the permission in the select, Joomla! tries to start an AJAX request, but it encounters an error in /media/system/js/permissions.js building the parameters
to be sent to the server.
The error message is

 document.getElementById(jform_title) is null.

Like you can see reading the Javascript file, or like it is said in the page of docs.joomla.org linked before, Joomla! expects a field named "title" in the form (more specifically, an element with id "jform_title"
and a "value" property"). Categories, user groups, etc., all have a field named "title", and everything works.

I'm sorry if I'm not being clear.

Hi,
I think I understand you and will try to fix this issue in the next week (together with a few others). Thanks.

Fixed in coming 3.2.64.