Storyline 360 Freezes when I try to Insert Anything

I'm relatively new to SL and have been having an issue with it freezing, i.e. I click on the menu for the thing I want to insert, the cursor spins.... nothing happens and if I click the cursor at all, it rings as if it's a mistake.

Last week, it was when I tried to insert a Graded Question. I managed this in the end, but I'm not sure how!

Today, numerous times,  it is when I try to insert an icon. I have inserted a whole bunch of icons into the same project last week with no issue, but now I need to add one as feedback for my client, it's not working.

I have followed guidance on other threads of uninstalling SL, rebooting laptop, re-installing SL, rebooting laptop, but no joy.

I have tried doing the task in a new project, but no luck either. 

In order to do anything else, I have to open Task Manager and close SL entirely.

Please help.