Can not upload pictures

I am having the same picture uploading error issue.
I just started to design the front page slider and wanted to upload pictures for that.
I could upload two pictures without any problem than by the third one I get an error message: Can not upload – working library is missing……
This happened first two days ago
Than I loged out and opened again just next day
Again the same after the 2nd picture received again this error message of missing library.
I am using WP version 4.4.2 and did not give even any try for update to 4.5
I cleaned cache and deactivated my plugins.
I have only 4 pictures uploaded for the favicon and for the logo.
Until this time I did not do any coding did not touch any single lines in CSS.
I would love to use this theme really do not want to change for any other because I love this theme.
Would appreciate some help especially that I am running race of the time because I do have a deadline.

Thanks for any help

Judit