Unable to unzip Omeka file

We have downloaded Omeka to our server but cannot unzip the file despite installing unzip to Ubuntu. It appears the zip file is encrypted or password protected. Has anyone else had this problem?

We are using 7-zip to uncompress.

I just downloaded a fresh copy to make sure, and I had no trouble unzipping it with either a graphical zip tool or unzip on the command line. There is no encryption or password protection on the zip file.

Maybe there was some problem in your first download of the file? Try getting it again.

I think my company's firewall or desktop environment is somehow affecting the zip file. I was able to download onto an alternate computer with no problems.

Thank you greatly for your response/help!