You can no longer use scanning with Finale. that was removed in F25. My suggestion would be to purchase the full version of SmartScore or other scanning program. (I use SmartScore Pro.) DO NOT be misled into buying the Music-to-XML version. There is a learning curve involved, but the time is worth it.

You can find numerous threads in this forum about scanning.

Depending on how long ago you lost your earlier computer, you should check your account at MakeMusic to see if you could download an earlier version of Finale (like Finale 2014.5 if you owned it) which would give you rudimentary scanning ability. This is not to say you cannot (should not?) upgrade to Finale v25, but an earlier version--if you owned it and it will still work with your current computer--could give you rudimentary scanning ability.

(While I do not doubt for a minute Mike's assessment of SmartScore Pro, which I own, I do not do enough input via scanning to take the time to learn the program's in's and out's; so I do my clean-up in Finale even though it likely would be easier if I learned SS Pro.)

… I have a Mac, latest version High Sierra …

There are well known compatibility issues between the earlier Finale versions (like e. g. Finale 2014.5) and the latest version Mac OS High Sierra.

Either

keep the earlier Finale version - and downgrade Mac OS,

or

keep Mac OS High Sierra - and upgrade Finale to v25.

I would upgrade Finale.

The only way for 2014.5 to work in High Sierra at all is to downgrade to an earlier OS, install and authorize it, then upgrade the OS. It will perform the same way it does in Sierra—with limitations. 

SmartScore X2 Pro costs $199 for Finale users when purchased through the MakeMusic Store.

What is your time worth? 

SmartScore Lite requires you to download and install Java 6 Run Time from Apple. It’s a free download. I forget if the Pro version also requires it.  

https://support.apple.com/kb/dl1572?locale=en_US

THANKS EVERYONE>> 

Gary