Turns out to be a bug introduced in the Windows versions of R2024b update 7 and R2025b update 2. If your PATH environment uses expansion of %SYTSTEMROOT% - i.e. contains things like %SYSTEMROOT%\System32, then these updates no longer correctly expand. Therefore, internal calls to things like cmd.exe and rundll.exe will fail. Since this is the mechanism used by Matlab to call up the browser for the doc command, then the doc command fails.
The workaround is to edit your PATH environment variable, and explicityly expand the use of %SYSTEMROOT%, so that your path variable explicitly contains C:\Windows\System32 and others, as appropriate to your particular Windows installation.
That fixed the problem for me. Bug reported.
