I have recently purchased a new computer and have downloaded sketchup 2017 as well as my normal up to date pro 2019 version as I use the 2017 version to send models to engineers etc which they can read with make. However I cannot register the 2017 version with my original licence details. Does this mean that afte 30 days it will become unusable?
Save as to 2017 within 2019, no need to have 2017.
It sounds like the Engineers require a Pro licence since they’re using SketchUp for commercial purposes.
Yes. When you receive a license for a new version of SketchUp you can no longer activate the older version on a new computer after you have activated the newer one.
The 2017 Make version will continue to work, but as others have already noted, you are not allowed to use it in your business. This also is the case with your engineers. If the only thing they need to do is to view your models, they could install the free SketchUp Viewer instead.