Hi there Stephen and welcome
Can you please attach the word file to this question and I can then check it and see what the issue is.
ok, looks to be your copy of word that has the issue as the file is working fine for me when left text-aligning
What I want you to do is a reset of Word, to do this, go to this link
Click on Download and download and run the file.
Complete the process and when you have, restart and tell me please if you still have the issue
ok, but you only needed to run a file, which you did in a roundabout way (the program you had installed would have ran the file for you).
Though my instructions where no more complex then installing pcmatic or running any file on your computer.