Cannot access Ubuntu in multi boot on laptop with Windows 10 after installing Ubuntu

Before installing Ubuntu on a laptop with Windows 10 I first attempted to install the Raspberry Pi OS. It failed and left this error:

g2ldr.mbr

0xc000007b

file missing or contains errors

I tried repairing the Raspberry Pi OS installation but this made no difference.

Started again by installing Ubuntu. Completed installation, restarted, removed install USB, laptop started and same error as before. Ubuntu was not added to the multi boot menu.

How can I fix the multi boot to run Ubuntu and then fix the Raspberry Pi OS installation from there?

Thank-you.