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What actually happened is this: Ι created a voki presentation and uploaded it on my moodle elearning platform. A few days later I changed my mind about some of the slides so I went back on my voki account and deleted some of the slides and changed the voice text and the backgrounds in others. I saved the new version and I clicked to get the new url.  I uploaded the new url and clicked to play the presentation but to my surprise it was the old version that I came up with. Thinking that I had done something wrong I repeated all the steps -save-get url-upload etc but it kept playing the old version. I also tried to share the presentation on messanger or on my address bar, just in case it was moodle's problem. but again it copied the old version. Right before receiving your reply to my initial message in one my desperate attemps to copy paste the url I managed finally to come up with the new version.

Anyway, I intend to create and upload on my website more presentation the next days and I 'll let you know if this happens again. . 
Once again thanks for your consideration and assistance

Wow! Thanks for your immediate reply! Well, I think that I managed to do it finally, don't ask me how though I have no idea, I think after several tries I managed to come up with the right version. Could it be that it takes some time for the url to be updated when we save a presentation?