I had an issue similar to this:

https://pdn.pega.com/support-articles/unable-access-prsysmgmt-tomcat

The error was that the "struts-tags" library was not found when attempting to add a new Pega node to SMA.

I had disabled JAR scanning in Tomcat, which is required for the SMA Struts annotations to correctly load the tag lib.

I was tipped off by this article: https://stackoverflow.com/questions/38799491/error-with-struts-2-when-i-use-tomcat-8-jre-1-8?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

Hope this helps someone else!

Cheers,

Nigel

***Updated by moderator: Lochan to tag post as Knowledge Share and mark as discussion.***