If you copied the files over a previous installation and then changed the connection string to a new db its possible you have an extra script in the /Setup/applications/mojoportal-core/SchemaInstallScripts/mysql folder
There should only be one script in this folder, if there is more than one then delete all except the highest version and start again with a clean db.
The logic is if mp_Sites table doe not exist then first run scripts from the above folder (but as I said there should be only one)
Then it will run additional scripts from the /Setup/applications/mojoportal-core/SchemaUpgradeScripts/mysql folder if the any exist with higher versions
Hope it helps,