This message pops up because the OMS software is not registered in the Apple Store, but the software is up to date and safe to download.
Use the guidance below to continue through the pop up (note that it will still appear each time).
Do not double click on the file to open it
Go to Finder > Downloads
Right click on the OMS file
Select Open from the pop up menu that appears
The "Verification" process can take up to a few minutes
Click Open or Continue on any subsequent messages that pop up (even if the option to Open is greyed-out)
