Hi Brian, just saw your question here. I've seen this caused by JAR file conflict in a few projects recently. Essentially you end up with more than 1 JAR file in your userlib folder that provides the same class. One of them is an older version and doesn't have the method above.
Here's one forum question about it: https://forum.mendix.com/link/questions/87149
And another that I commented on recently, with some instructions on how to find the problem JAR: https://forum.mendix.com/link/questions/88190
File a bug report. I have never seen this error. Looks like an after startup error of the SAML module. The only thing I can think of is checking your userlib on duplicate libraries.
Regards,
Ronald