I tried to:
1. Remove Premiere Pro preferences file
2. Restore Premiere cache while Holding shift while opening the program.
Then I I exported the whole sequence for the third time. The same thing happened. The export process never gets to mux the video and audio files. All I am left with in my output folder is the video and audio file separately and an extra mp4 file, which size is 0 bytes.
I really need a solution for this. I don't mind to pay for it if necessary.