Your users created in Cognito User Pool admin console will automatically receive a FORCE_CHANGE_PASSWORD status flag. For some obscure reasons, you as an administrator cannot confirm the user yourself using the Cognito User Pool admin UI.

By far the quickest solution is to use AWS CLI:

aws cognito-idp admin-set-user-password \
--user-pool-id <user-pool-id> \
--username <username> \
--password "<password>" \
--permanent

You might need to upgrade your AWS CLI before you will be able to run the above command:

pip3 install awscli --upgrade