Hi, @Dmitriy Velikanov
Thank you for posting in Microsoft Q&A forum.
If we do not enable the Active Directory User Discovery, when we query sms_ad_user_discovery_agent, it will show "error communicating with component". So we may double check we did have enabled the Active Directory User Discovery.
We may also try to check adusdis.log for more details.
By the way, SCCM 1902 ended support on Sep 27, 2020, it's recommended to upgrade it to version 2107 as soon as possible.
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