I was integrating our corporate JIRA with One Identity Cloud Access Manager via SAML2. I chose the plugin from Resolution GmbH.
Integration was a breeze. Their wizard is brilliant! I got the whole integration completed successfully within 15 minutes.
One issue I encountered was - "SAML-message with NotBefore xxx is not valid yet."
This was quite easily resolved. Do make sure the IdP (One Identity Cloud Access Manager) and SP (JIRA) are sync-ed with the same NTP server.
The error disappeared as soon as I have NTPd configured on my JIRA server.