There are several possible reasons your user(s) may be having trouble accessing ML Schedules with their Active Directory credentials. You will want to take the following steps to figure out the root of the issue:
1. First, determine if the issue is with ALL Active Directory accounts or only some.
If ALL users continue to Step 3.
2. If only specific users, the issue is most likely users typing invalid login credentials, so confirm the users are entering their AD username (not email) and AD password. If they do not know this information, whoever manages your Active Directory account can reset it for them. We do not store Active Directory passwords and we do not have access to change this for them.
3. Confirm with your webmaster that they have allowed the Following IP Addresses to connect to the Active Directory Server and opened port 636 (port 389 is optional):
Important: Please make sure ALL IP addresses are types accurately and no numbers are missing.
4. If step 3 is confirmed and issues persist, re-establish your connection through the AD Connection page (under Settings > Active Directory > AD Connection), by re-entering the Admin level AD username (not email) and Password and testing the connection.
IMPORTANT: If the connection still fails, that means something on the firewall is configured incorrectly. Confirm once again that both ports are open and all IP addresses are allowed and listed correctly. If everything is listed correctly on the firewall, send a screenshot to firstname.lastname@example.org of all IP Addresses listed for assistance troubleshooting the issue further.