Hello Jorge,
I didn't modify the example code. I just imported DSPI polling example and DSPI interrupt example on MCUXpresso 10.0.2.
I have a channel of a scope on MISO and another on MOSI.
In DSPI_polling_transfer
First of all I imported SDK example with "Import SDK Example".
Then I start debugging but it opens "startup_mk66f18" file, and mouse cursor is put on Hardfault_Handler...

Then when"DSPI_SlaveTransferNonBlocking(EXAMPLE_DSPI_SLAVE_BASEADDR, &g_s_handle, &slaveXfer);"
fonction line is executed nothing appears on the scope and transmission registers are empty (0x0).
Then when "DSPI_MasterTransferBlocking(EXAMPLE_DSPI_MASTER_BASEADDR, &masterXfer);"
fonction line is executed something appears on the scope and TX registers are full but RX registers are full of 0xff.

Clock issues ?
Therefore in my opinion this code only works to send data from the master.
In DSPI_interrupt_transfer
After "DSPI_SlaveTransferNonBlocking(EXAMPLE_DSPI_SLAVE_BASEADDR, &g_s_handle, &slaveXfer);"
I have this:

So slave transmission should be good.
And after "DSPI_MasterTransferNonBlocking(EXAMPLE_DSPI_MASTER_BASEADDR, &g_m_handle, &masterXfer);"
I also have this :

And even sometimes I have 0x0 in RX registers for both files...
Maybe these codes allow transmission. However it doesn't seem to work perfectly for me...
Do you have an idea?
Could you please send me your file?
Best regards,
Benjamin Heder