Check to see if the account you are trying has the user login name correct with the correct @domain.com (Under account tab when you bring up user properties in AD), this is the username that it uses for login.
We are just now starting to use the LANDesk MDM and, in our case at least, the login accepts two possible combinations.
"domain\username" which is what the employees use to login to their computers
"username@full domain name" For this the full domain name is what we use when adding a system to the network.
What we use for "domain" is different than what we use for "full domain name". When using the format domain\username I found to get the \ character you have to tap and hold on the / character and it will show \ as an alternate.
If LANDesk is tied into AD then the same logins should work.