Hi. I have a 2018 Pro licence. I was running on MacBook Pro 2015, which died, so can’t open it to retrieve my licence codes to be able to access Sketchup on my new MacBook Air.
Thanks in advance for any pointers/assistance…
You should have received the classic license info by email (when you bought it). Try to find that email. If you have your serial number and email address, you can get an authorization code from here:
License Manager
(I’m not sure if it still works…due to End of Support policy.)
However if you activated that licence more than 2 computer, or the above thing does not work, perhaps @colin can help you…
Also, you have a good chance that there will be compatibility issues: Sonoma 14.3 <> SU2018… 
You do have a SketchUp 2019 license that you didn’t yet use. I have sent you a message with both licenses.
HUGE Thanks for that - @colin a great help also. Am back sketching and printing…
Thanks Colin. All worked. Tickety-boo!