The company file you have selected is an MYOB company file...

Troubleshooting Alert Messages Overview > Alert messages (in alphabetical order) > The company file you have selected...
If you haven't already done so, we suggest you read the Troubleshooting Alert Messages Overview.

Situation: The company file you attempted to open is a version previous to the current version and it can't be used by MYOB Accounting Plus Version 11 in its present form.

Solution: Be sure the company file you attempted to open is the company file you want. If you're sure the file is correct, you'll need to upgrade the company file using the MYOB Accounting Plus Upgrade Assistant.