Unable to Edit SAML App Settings - Error "We found some errors. Please review the form and make corrections"

When attempting to edit/save any setting of a SAML app in Classic, the following error is encountered:

Invalid expression syntax {expression}

In OIE, the error seen is the following:

Please use the SpEL expression syntax to write expressions.

• SAML App

The issue is caused when using an old deprecated expression language format for the Application username format.

Review the expression used for the Custom Application username format and replace it with the new format of Okta Expression Language:

• Okta User Profile