would like to access data from other apps

macOS Sequoia has started to fully control security.

It's about App Groups in xCode.

The developer of this application in xCode in the section:

Signing & Capabilities → Targets → TARGET_NAME → App Groups → App Group

should have specified:

$(TeamIdentifierPrefix)myFirm.myName

and not a made-up ID (for example, "myGroupID.myFirm.myName").

And in the program code it was necessary to specify the real ID of the group (in numbers)

let storeDirectory = FileManager.default.containerURL(
    forSecurityApplicationGroupIdentifier: “0123456789.myFirm.myName”
)

After recompiling the application, the problem disappears.

I recommend creating a bug report on this developer's page.

You may be better served by switching from Seagate Toolkit Sync to CCC - Carbon Copy Cloner. It will do a better job of sync'ing your backups. Otherwise you need to wait for Seagate to fix their broken Toolkit Sync software.

Carbon Copy Cloner 7 is fully macOS Sequoia compatible and it uses APFS and snapshots and gives you far more control over your backups.

You could also use Time Machine which is free or a combination of rsync & RsyncUI a macOS GUI app frontend to the command line rsync utility.

I would add that these maintenance apps provided by companies such as Seagate, often cause problems. I recommend removing them completely. Incidentally, I use and can recommend Carbon Copy Cloner. It has advantages and features not found in Time Machine.

Seagate is aware and have offered no update for a resolution even though you have other options that have been recommended that don't cause the problem you are seeing with the Seagate Toolkit.

https://www.seagate.com/support/kb/toolkit-would-like-to-access-data-from-other-apps/

As I mentioned, such maintenance apps often come with new disks. Those apps should never be used. The best thing to do when you receive a new disk is to use Disk Utility to erase and reformat the disk before using it.