You need to do the proforma the clients from the 2018 program. In the 2019 program press F10 and look at system file path. When in 2018, do another proforma and verify the system file path for 2019. 

I would NOT do all of them now, as the program is notorious for having many flaws this early in the game. I do my return only and start to play with it for this year. There are also demo clients you can access from a RESTORE from C:\LACERTE\19TAX\DEMODATA\ that are a good practice. Be sure the SSN (or EIN) is all 9's and there will be no REP charge. 

You also do the Organizer for 2019 from the 2018 program. I would NOT do all of them now, as the program is notorious for having many flaws this early in the game.

I have been doing this for 10-years so I know that the file path is correct.  In fact, all of the other tax types transferred over fine (partnership s-corp, fiduciary, etc) just the individual did not.

OK...

Maybe explain what "the system thinks it did" means?  

@andrewfoxcpa are all the 2018 clients locked?

I thought of that...but then they just don't transfer, right?  I'm confused by what "the system thinks" means....
But I've only been doing this for 3 decades...so whadda' I know

Ours did the same thing, on Individual only.  It appears to go through the motion of transferring, but all that shows up are the client numbers.  If I click on one of those I get an error message that the detail file is missing or damaged.  All other modules are fine.