Hi HomerJ,
Yes, if an issues arises or changes were made to the LDAP system then this can stop/ hinder the authentication process of ALM. I would recommend that in order to identify the issue try and see if anything is written within the log file (there maybe not be anything there if the services are in error): Here is the default location for the log files: C:ProgramDataHPALMlogqc There is also a C:ProgramDataHPALMlogsa that is the site admin log files.
If you have multiple LDAP servers and one was moved, taken offline (even temporarily) etc, then the connectivity would be broken and then usually the only way to re-establish the connectivity is to change the authentication to QCAUTHENTiCATION within the DB (specifically within the qc_siteadmin_db schema within within the configuration table and then restart the server and then reestablish the connectivity through the LDAP setup in the site admin. To do so you will need the site admin account and password that was used to install the software originally (I have uploaded the document that details the steps to perform). If you have another admin that can log in then you can try and have them log in and check on your user account in the site users tab as well and also check on the LDAP configuration and reestablish the connectivity that way hopefully.
Hope this helps. If you have the log file you can see if any error exists and provide that to your support team for further assistance with this issue.
Dan