Make sure you have your Base Serial number and Registered Name before you start. Be aware editing the registry can cause serious issues on your PC if you modify settings or delete something by mistake.
Make sure that your printer is set to A4 paper size by editing the printer properties.
In Pastel, go to File>Printer/Fonts Setup, click on “Set Printer” & select your printer from the list. Finally, click “Copy to All Tabs” to make this printer default in Pastel
Make sure your password conforms to your version of Pastel. Change the password to contain both letters and numbers & see if that helps.