The SHRINE hub received a response from an adapter that it could not interpret.
SHRINE expects XML messages that comply with the i2b2 messaging protocol. If a site is improperly configured, it may respond with plain HTML error pages instead of i2b2 XML responses, which will naturally cause the i2b2 message parser to fail.
A RootTagNotFoundException (1.22 and later) may indicate that the adapter is sending a plain-text reply with additional error information in the plain text. Earlier versions of SHRINE may report an Exception with "Didn't recognize root tag name ..." inside a ProblemNotYetEncoded.
If you are a user, supply all details to your site admin who can work with the adapter admin to resolve the issue.
If you are the adapter admin, examine the details, especially the response body, to help determine what is wrong. The response body is very likely a message from Tomcat that will give you some insight into the problem.
If the adapter is sending plain text and the hub reports this problem then the adapter may be on version 1.19.2 or earlier.