Unable to change iTunes Media folder location

Installing iTunes on a new PC. iTunes v12.9.6.3, from Windows Store. Windows 10 Pro 64 bit v1903.

I am unable to point iTunes at a new location for the iTunes Media folder (the external drive from my old computer with my iTunes library)).

I change the library location in Advanced Preferences. However, when I exit, then re-launch iTunes, it has reverted to the default location (c:\users\.....).

Any ideas how how to make the library location persistent?

Thanks.