Hi @wodudwo
IVT offset 0xC is not used to start AppBL (application covered by Basic Secure Boot). This is a pointer to vector table of application which is supposed to be started on core 0 when secure boot is not enabled by BOOT_SEQ bit.
IVT offset 0x14 is not used to start AppBL either. This is a pointer to vector table of application which is supposed to be started on core 1 (if available on a derivative).
IVT offset 0x30 is used as a pointer to app header of AppBL. This is used when secure boot is enabled by BOOT_SEQ.
See “Table 118. IVT structure” for details.
Screenshot from "S32K344_Basic_SecureBoot" mentioned below:

Another point is that start address of application must be aligned to 128 bytes. And there must be 64 byte app header before the application.
I recommend to check following resources:
HSE DemoExamples:
https://www.nxp.com/webapp/Download?colCode=S32K3_HSE_DemoExamples
Take a look at projects:
This one configures the basic secure boot:
c:\NXP\S32K3_HSE_DemoExamples_1_0_0\S32K3_HSE_DemoExamples\Secure_Boot\S32K344_Basic_SecureBoot\
This is the application which will be executed once secure boot is enabled:
c:\NXP\S32K3_HSE_DemoExamples_1_0_0\S32K3_HSE_DemoExamples\Secure_Boot\S32K344_SecureBootBlinky\
Secure Boot application note including demo projects. It can be downloaded from:
https://www.nxp.com/products/S32K3
Application note can be found here:
Documentation -> Secure Files -> Secure Boot Application note v0.1.1.0 (AN744511)
Associated demo project can be downloaded here:
Design Resources -> Software -> Secure Files -> SecureBootAppNoteDemo (SW745310)
Take a look at “5. Basic Secure Boot”, especially the last part of “5.2 Configuration” which talks about the alignment.
Regards,
Lukas