I wanted to load my custom packages using 14.1, but the packages cannot be loaded, and I get the error message:
"Cannot open MyPackage`.
What can I do?
With Mathematica 14.1 now called Wolfram 14.1 the application directory has moved, as explained in the documentation: Upgrading from Mathematica to Wolfram. Fortunately (of course you have a backup) the packages are still in the old directory folders.
The new place for your packages on Windows is now:
C:\Users\myname\AppData\Roaming\Wolfram\Applications
and the old place was:
C:\Users\myname\AppData\Roaming\Mathematica\Applications
Just move your files from the old to the new directory.