This has been reported by an RH-SSO 7.1-Beta Customer via KEYCLOAK-4642 which the customer opened himself.

See- KEYCLOAK-4642
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Offline tokens do not seem to be supported in client admin.
I am aware that offline token is nothing more than a normal refresh token which does not expire.
In this sense, offline token is going to replace username and password and should be treated as an input config parameter.

org.keycloak.admin.client.token.TokenManager assumes that refresh token can only be generated by itself. It does not accept offline token as a config parameter.
I have updated to code, to temporary continue with I am doing.
If the problem is valid, I can create a pull request with a proposal on how it can be fixed.

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