 on failure. If the base64 couldn't be decoded then olm_session_last_error will be &quot;INVALID_BASE64&quot;. If the message was for an unsupported protocol version then olm_session_last_error() will be &quot;BAD_MESSAGE_VERSION&quot;. If the message couldn't be decoded then then olm_session_last_error() will be &quot;BAD_MESSAGE_FORMAT&quot;. If the message refers to an unknown one time key then olm_session_last_error() will be &quot;BAD_MESSAGE_KEY_ID&quot;.</p></dd></dl><dl><dt class="spec value" id="va