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Please check the following article on how to do both things: Approve Teams app
App can’t be installed → Something went wrong / permissions needed
When a user or even a group owner/teams admin is trying to set up the app he’s sometimes receiving one of the following messages:
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Even when the consents are set correctly in Azure AD and the permissions have been granted it won’t change the error message and the app can’t be installed.
In some cases the group owner consent has been turned off in Azure which causes to block the installation process. To enable it, please follow these instructions: https://yasoon.atlassian.net/wiki/spaces/M365fJ/pages/2330986746/Deployment+Microsoft+Teams+app#Allow-team-owners-to-install-apps-by-themselves
App missing from search
In case you can’t even find the app in search, your administrator probably has disabled all non-approved apps. To get the app approved and added, you’ll need to contact a Microsoft Teams administrator (through your normal IT support).