My Collection is not available - object library is not loading (Prezi desktop)

Hi there

Has anyone experienced sudden disappearance of "My Collection" object library?
I've been working away with mine absolutely fine, but suddenly it's gone...
When I re-open the prezi I'm working on it doesn't give me the option to save new objects into My Collection, neither can I access previously saved items from My Collections. The error message I've got is saying

"We could not load your object library. Please reload your prezi."

But closing and opening doesn't seem to make any difference...

Anyone have a fix for this?

Ta,
Krisztina