Upgrading SLES 12.5 to 15.5 Error

m trying to upgrade a VM server from sles 12 SP5 to 15 through a boot from a virtual CD ( [SLE-15-SP5-Full-x86_64-GM-Media1.iso] But im getting this error after boot, and initial load:
Any pointers would be appriciated

Internal error: private constant Y2Package ProductUpgrade MAPPING refrenced.

So you’re booting from the virtual media to do an offline upgrade but at what point does it display the above error? Are you able to choose Upgrade from the boot menu (after the welcome screen)?

Yes, exactly. I get through the welcome screen, choose upgrade, and once it reaches “performing upgrade” i get that error. If i then chose “abort” it goes back to simple install upgrade. . it tries once more and then i get , i brifely see the "looking up local registration servers " before it pops up.

Sorry for the delay in replying. I’m no expert here but I’m guessing from the “Previous snapshot was not found” bit of the error message that your server is using the Btrfs filesystem and I’m wondering if all your snapshots are okay.

Presumably you can still boot your VM as SLES12 SP5? If so, what does “snapper list” report?