MikTex just won't compile (errors from miktex-pdftex.exe, miktex compiler driver, memory dump file)

Question

My problem is that no document compiles on MikTex, not even the simplest HelloWorld article. The error is Sorry, but "C:\Program Files\MiKTeX 2.9\miktex\bin\x64\miktex-pdftex.exe" did not succeed. Apart from these, sometimes (while trying to compile other documents) I also get the error Sorry, but "MiKTeX Compiler Driver" did not succeed. Note that I've changed the compiler from pdfLaTex+MakeIndex+BibTex to only pdfLaTex as well.

I'm sorry for asking this question here again since so many have already asked it. However, none of the answers on the other questions works for me-I've tried them all. Specifically, I've uninstalled and reinstalled entire the MikTex application, have allowed full control of the installation and users/AppData/local/temp directories, tried compiling the HelloWorld document multiple times, restarted my PC, updated the database through the MikTex Console, etc.

My setup is a PC running Windows 10, and I've updated my MikTex 2.9 version to the latest (this was a fresh installation anyway). Any help on this matter is highly appreciated, I have included the log file below.

2020-06-15 11:23:04,162+0530 INFO  miktex-pdftex - this process (5304) started by 'miktex-texworks' with command line: "C:\Program Files\MiKTeX 2.9\miktex\bin\x64\miktex-pdftex.exe" -synctex=1 -undump=pdflatex hello.tex
2020-06-15 11:23:04,166+0530 INFO  miktex-pdftex - allowing known shell commands
2020-06-15 11:23:04,166+0530 INFO  miktex-pdftex - enabling input (output) from (to) processes
2020-06-15 11:23:04,185+0530 INFO  miktex-pdftex - going to create file: pdflatex.fmt
2020-06-15 11:23:04,210+0530 INFO  miktex-pdftex.core - start process: initexmf --enable-installer --dump-by-name=pdflatex --engine=pdftex
2020-06-15 11:23:04,525+0530 INFO  miktex-pdftex - this process (3116) started by 'miktex-makefmt' with command line: miktex-pdftex.exe --miktex-enable-installer --miktex-disable-maintenance --miktex-disable-diagnose --initialize --interaction=nonstopmode --halt-on-error --alias=pdflatex --job-name=pdflatex -tcx=cp227.tcx --enable-etex pdflatex.ini
2020-06-15 11:23:04,529+0530 INFO  miktex-pdftex - allowing known shell commands
2020-06-15 11:23:04,529+0530 INFO  miktex-pdftex - enabling input (output) from (to) processes
2020-06-15 11:23:05,675+0530 INFO  miktex-pdftex - this process (3116) finishes with exit code 1
2020-06-15 11:23:05,675+0530 WARN  miktex.core - still open: "C:/Program Files/MiKTeX 2.9/tex/latex/00miktex/pdflatex.ini"
2020-06-15 11:23:05,675+0530 WARN  miktex.core - still open: "C:\Program Files\MiKTeX 2.9\tex/latex/base\latex.ltx"
2020-06-15 11:23:05,675+0530 WARN  miktex.core - still open: "C:\Program Files\MiKTeX 2.9\tex/latex/l3kernel\expl3.ltx"
2020-06-15 11:23:05,675+0530 WARN  miktex.core - still open: "C:\Program Files\MiKTeX 2.9\tex/latex/l3kernel\expl3-code.tex"
2020-06-15 11:23:05,675+0530 WARN  miktex.core - still open: "C:\Program Files\MiKTeX 2.9\tex/latex/base\ltexpl.ltx"
2020-06-15 11:23:05,714+0530 ERROR miktex-pdftex - C:\Program Files\MiKTeX 2.9\miktex\bin\x64\initexmf.exe did not succeed; exitCode: 1
2020-06-15 11:23:05,714+0530 ERROR miktex-pdftex - output:
2020-06-15 11:23:05,714+0530 ERROR miktex-pdftex - 
Sorry, but "MiKTeX Configuration Utility" did not succeed.

The log file hopefully contains the information to get MiKTeX going again:

  C:\Users\Aritra Das\AppData\Local\MiKTeX\2.9\miktex\log\initexmf.log

2020-06-15 11:23:05,714+0530 FATAL miktex-pdftex.core - The memory dump file could not be found.
2020-06-15 11:23:05,714+0530 FATAL miktex-pdftex.core - Data: fileName="pdflatex.fmt"
2020-06-15 11:23:05,714+0530 FATAL miktex-pdftex.core - Source: Libraries\MiKTeX\TeXAndFriends\texmfapp.cpp:692
2020-06-15 11:23:05,715+0530 FATAL miktex-pdftex - The memory dump file could not be found.
2020-06-15 11:23:05,715+0530 FATAL miktex-pdftex - Info: fileName="pdflatex.fmt"
2020-06-15 11:23:05,715+0530 FATAL miktex-pdftex - Source: Libraries\MiKTeX\TeXAndFriends\texmfapp.cpp
2020-06-15 11:23:05,715+0530 FATAL miktex-pdftex - Line: 692
2020-06-15 11:23:05,715+0530 INFO  miktex-pdftex - this process (5304) finishes with exit code 1

EDIT1: Upon suggestions made in the comments, I have run the command miktex-pdftex.exe --initialize --halt-on-error --alias=pdflatex --job-name=pdflatex -tcx=cp227.tcx --enable-etex pdflatex.ini and get the following error in the command prompt.

! LaTeX3 Error: File 'UnicodeData.txt' not found.

For immediate help type H <return>.
 ...

l.28130   }

!  ==> Fatal error occurred, no output PDF file produced!
Transcript written on pdflatex.log.
miktex-pdftex: major issue: So far, no MiKTeX administrator has checked for updates.

Consequently, I checked the console to find that UnicodeData package is already installed so I don't know what's throwing up this error.

Answer 1

I had a very similar problem after a fresh install of MikTex 2.9. I initially traced it (not very forensically) to the pdftexcmds package, which seems to have been updated recently, but thought no more of it until today.

I did a clean install of MikTex 2.9 today and, when prompted for updates at first launch of the MikTex Console, I unticked pdftexcmds (which is marked as optional). This has solved the problem for me and pdflatex is working again.

Interestingly, running pdflatex now says that it is MikTex 2.9.7440 whereas it said MikTex 2.9.7441 after updating pdftexcmds. Unfortunately I don't know anymore of the inner workings of MikTex to go on from here.