Hello
it is quite annoying but i believe that is happening the reason of the package name for PPC ( powerpc) have changed.
Example:
For the 6.xx version the package name is routeros-powerpc-6.xx.xx.npk
https://download.mikrotik.com/routeros/ ... 6.48.6.npk
For the 7.xx version the package name is routeros-7.2.2-ppc.npk
https://download.mikrotik.com/routeros/ ... .2-ppc.npk
The only solution is to run the upgrade for this architecture, for now, by downloading the routeros-7.x.x-ppc.npk on your PC and the uploading it to the router.
After the file is uploaded reboot the router to proceed with the upgrade.
Best Regards,
Daniel