Last week, the font suddenly changed to a bigger font and although the output screen on the computer showed it perfectly, when it got to the TV screen the sides were cut off and words were not showing..... only on large scriptures.
We have tried c hanging the font size, changing the screen size, changing the margins adn nothing has worked.
I am not very technically minded but have tried everythign I can think of and cannot fix it. We also can't work out how it was working perfectly and then suddenly it had changed.
Can someone please help?

Sounds like Windows is reading the Screen Resolution incorrectly. You need to change that in Windows rather than in EW.  Right click on the Desktop of the main control window and select Display Settings. Make sure that the resolution on the display having the issue is set to the correct resolution. 

This is a fairly common issue if you are using an overhead projector and/or an HDMI cable over 30 feet or so without using a signal booster or an active cable.