Explanation/Reference:
Explanation:
Before you can configure SSIS to enable support of AlwaysOn on the new added secondary Replicas, you must connect to all new added secondary replicas.

Note: To use SSIS with AlwaysOn, you'll need to add the SSIS Catalog (SSISDB) into an Availability Group. You'll need to do the following steps:
Make sure you meet the prerequisites for using AlwaysOn

Connect to every node and create the SSISDB catalog. We need to create the catalog even on

secondary nodes to create the other server-level objects (cleanup jobs, keys, accounts etc) that are used by SSIS.
Delete the SSISDB databases on secondary nodes.

Create an availability group, specifying SSISDB as the user database

Specify secondary replicas.

References: https://chrislumnah.com/2017/05/09/enabling-alwayson-for-ssisdb/