To correct changed netnames back you will need to have:

• Corrected DSN file , with correct net names. Let’s say we have VCC power net in DSN, but our board file got VCC_536261 from previous incorrect DSN net in import.
• Created netlist from that fixed DSN file.
• Board file which we need to correct.

STEP 1.

• Open board file in Allegro PCB Designer.

STEP 2.

• Select function Logic > Net Logic…

STEP 3.

• Delete duplicated VCC net

STEP 4.

• Rename VCC_536261 to VCC and select any correct pad with proper net to be assigned

STEP 5

• All shapes and structures should be updated to VCC netname now.

STEP 6.

• Now import netlist from DSN. VCC netname should stay intact.