I found my issue -- noted it down here for reference if anyone has this issue in the future:
"The 'file not found' message is typical of what you see when Windows Defender Controlled Folder Access is turned on and has just blocked changes. Either add the app you are saving from to the list of apps allowed through controlled folder access or turn off the protection."
Allow a blocked app in Windows Security
Controlled folder access in Windows Security reviews the apps that can make changes to files in protected folders. Occasionally, an app that is safe to use will be identified as harmful. This happens because Microsoft wants to keep you safe and will sometimes err on the side of caution; however, this might interfere with how you normally use your PC. You can add an app to the list of safe or allowed apps to prevent them from being blocked.
Select Start Windows logo Start button > Settings Gear-shaped Settings icon > Update & Security Circular arrows Sync icon > Windows Security > Virus & threat protection.
Under Virus & threat protection settings, select Manage settings.
Under Controlled folder access, select Manage Controlled folder access.
Switch the Controlled folder access setting to On or Off.