The TI-Nspire CAS+ P1-EVT2 has a different boot screen than later Nspire: So it probably has different Boot2 and Diags flashing screens too.
I hope you're making sure there is no diags present before testing the diags reflashing combination, as it immediately erases diags before receiving any data (unlike the boot2 reflashing combination, which doesn't erase until the transfer is completed)
Yes,I had checked before. When using the diags combo on the P1-EVT2, we get an error in the bootlog:
Keypad request - launching DIAGS software...
Error reading/validating DIAGS image
Error loading DIAGS. reverting to BOOT2.
Up to now, I've never found a CAS+ including a Diags image