I am stuck in a weird problem - 

My topology is 1 WFE and 1 App Server.

The users have been properly imported from Active Directory as they are visible when I search them in User Profiles in CA. However, all users are not visible in the people picker of the other Site collection on a separate web application in the same farm.

For example, take a user say John Davis - 

Going to CA and then if I try to add that user in CA itself, and I type his name in people picker, he is visible there and I can add him (although I won't as its CA). However, in the same farm I go to my site collection which is on a different web application (obviously), and if I try to share that site with him and type his name in People picker, I am not able to see his name. This is happening for many users :(

I googled and someone suggested to check the content DB syncs and I did that as well and the DBs show that they were synced today itself, so it is not related to that.

Please help!!!

thanks & regards,

Sangeet

Hi

For your issue, make sure the web application's service account is a domain account, go to Central Administration -> Security -> Configure Service Accounts, select the "Web Application Pool - PoolName" from the drop-down list, and that will display the service account associated with the Web Application Pool (and the user that is performing the Active Directory lookups).

Similar issue post for your reference:

https://social.technet.microsoft.com/Forums/office/en-US/db484046-1217-40da-a403-8f461095240a/no-active-directory-users-show-up-in-people-picker?forum=sharepointadmin

https://social.technet.microsoft.com/Forums/office/en-US/48fd24b8-62e5-405d-bd45-30e540bbea4c/forms-users-not-showing-up-on-the-sharepoint-web-application-people-picker?forum=sharepointgeneralprevious

Besides, here is an article about troubleshooting people picker issue:

http://www.sharepointtechs.com/active-directory-groups-not-showing-up-in-people-picker

Best Regards

Lisa Chen