.tex file that had been edited on Mac version of TexStudio and worked just fine doesn't run on Windows 10 TexStudio

I am using both Mac OS and Windows 10 to work on .tex files. On Mac OS it compiles and generates pdf file perfectly.

But when trying to run the same file on Windows 10 in the same environment (TexStudio), I keep seeing the errors: 1) Extra endgroup. begin{document}; 2) Missing begin{document}. begin{document}

I am definetely having begin{document} and end{document} in my code because it RUNS on Mac OS.

How can I run my .tex file on Windows 10?