very difficult to use Zoho

I just tried collaborating with someone on a document - it was totally impossible. The other person was able to open the document iin her web browser, but unable to edit it even though I had given her editing permission. And then, even after she had closed her web browser, I was unable to edit the document (of which I am the owner); I got an on-screen pop-up saying the other person was still editing the file. Collaboration is supposed to be easy! If Zoho is going to be an effective collaboration tool, it has to be much easier to use. I will not use Zoho again.