Upgraded TeXLive; pdflatex throws an error

[Rich Shepard]

I upgraded TeXLive from 2023 to 2024 and tried compiling the MWE for the
math issues still unresolve. A message box displayed:
The external program
pdflatex 
finished with an error. It is recommended you fix the cause of the external
program's error (check the logs).

1. Where do I find the appropriate log file? It's not in /tmp/ or /var/log/.

2. If LyX is looking for TeXLive2023 where do I tell it to look for
TeXLive224?

TIA,

Rich