If you are not able to log into the portal, verify the user is part of the groups or users defined in Site Security section
[Portal-URL]/admin/settings?category=user_administration_settings
If nothing is set. all users should have access but if groups and users are set- a match must be found to allow sign in. Group membership is checked against Active Directory live and not using local tables.
To verify that the user is a member of the groups set, you can use the following:
[Portal-URL]/admin/usersgroupmembership
In some cases you may be locked out because of setting saved that do not allow you to sign in and change them. Please refer here to solve this:
For cloud - Portal user locked out - Unlock Site Security for a SaaS client
For skype: Unlocking Site Security from the database
To find the location of your logs please open log4net.config file in the portal configuration folder:
and view the value of file parameter of RollingFileAppender: