Sometimes cryptic errors occur if there was a syntax error in a .bib BibTeX bibliography file that doesn’t disappear even when the .bib syntax is corrected. The fix for this is often to delete the auto-generated files:
- .bbl file.
- .aux file
Suppose the top-level LaTeX file is “main.tex”. Then the compilation generates main.bbl and main.aux among several others. If you keep getting errors when you know the syntax is correct then try:
rm main.aux main.bbl pdflatex main bibtex main pdflatex main pdflatex main
and see if that clears the error.