Sorry for not replying sooner. The problem was after installing the latest monthly update for PD365 the programme refused to open.
I wrote to Cyberlink Tech dept. who were pretty quick getting back to me. They gave me several options to try including...
1. Uninstalling the program through the application manager and re-installing it. Still didn't open.
2. Turning off all other open programmes including my internet protection software (Kaspersky). Then try opening it again.
Solved! For some reason, the programme was blocking Cyberlink which it has never done before, so after the monthly PD365 update it didn't recognise the newer version and blocked it.
Thanks for all the help.
Brian