Additional chat-related features and issues within Microsoft Teams for business
Hello RomaB23,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
Based on your post understand that from Teams app, when you go to “Chat” and from “Search” bar when you try to search user with “@username” (as per below screenshot) result show as not found. So based on it, we would like to confirm that if you open Teams web app via either Chrome or Edge browser does the same query occurs? If you haven’t check from there, kinldy check it.
If no issue from Teams web app side, kinldy check your Teams desktop client is updated with latest version. If it’s latest version, check with clear cache for the Teams app by follow the steps mention in Clear Teams cache - Microsoft Teams | Microsoft Docs.
If still same query or Teams web app side same situation, it is recommended that report this problem by open Teams app > go to Help > select Report a Problem. If you don’t have such option, kinldy contact your admin to report this problem. At this point, your kind cooperation will be highly appreciated.
Thank you so much for your precious time. Stay safe and healthy.
Sincerely,
Ankita Vaidya | Microsoft Community Moderator