Unable to set MOS credentials - OEM 13.5.0.20

New installation of OEM 13.5 RU20 on Rhel 8.9

MOS credentials are working

Setup -> Proxy Settings -> My Oracle Support -> Manual Proxy Configuration -> Test: Successful -> Apply

$OMS_HOME/bin/emcli set_mos_credentials -username="my_username" -password="my_password" -verbose_exception

Authentication Error: Please check your credentials: IO Error: Status code: 400, Reason: Bad Request, HTML:{"error":"invalid_request","error_description":"The request contains invalid parameters or values."}