Hi Robyn, The below is a copy of a post I've listed in a seperate thread.
For those who are experiencing issues with the altered paper size settings, an alternative workaround while the team are working on things on our end is to use the below settings. This will only need to be done once and the setting will stay in place beyond just the current session.
Customise the Template (either within Invoice or from List > Templates)
Go to Additional Customisation > Print
Tick 'Use specified Printer settings below for this Tax Invoice'
Choose A4 from Paper Size
Update all your template(s) and this setting will be retained.