This just may be me ... but ...
When I downloaded an attachment from this 'forum (wait.aslx) from a reply in my question. The first time I did so I chose 'run' during the download and I was only able to 'play' it .... but the next time, I chose to 'save' it (into my downloads) and in doing so, was able to edit it.
Thought I should point this out, if berat235 is still unable to 'open for editing'.
Cheers,
derekb