Config value invalid in this mode
This problem can happen when the network stream layer is configured. The configuration settings depend on the lower-level driver (e.g. plain tcp, GnuTLS) being used as well as the mode it is set to. For example, certificate-related config commands issued to the plain tcp driver (ptcp) are rejected. Similarly, some authentication settings can not be made when the GnuTLS dirver (gtls) is in anonymous mode.
The cause often is an invalid sequence of config statements inside rsyslog.conf. Remember that order of statements is vitally important. For example, one needs to set the driver first, before driver-specific commands can be issued.