How to revert back to a 2018 license

Hi,
We use a 2018 version of SketchUp in our company, wich is the only version compatible with a specific software (Trimble Scan Explorer).
Our active license is now the 2019 version, we automatically update, but now we can’t go back to 2018 version with ou 2019 serial license.
How can we downgrade and obtain a 2018 license ?
We purchased our perpetual license in 2018 so our maintenance & support license is expired.
Thank you for your help

you cannot activate an old license on a new system once a more recent version was activated already.

Existing program installations of old versions already activated before activating a new version are not affected, i.e. can be used further.

If a fallback to an old version because of e.g. an old plugin or operating system is required, the acitvation of the new version needs to be deactivated. Contact the supplier of your license for further information concerning this process.

Thank you for your answer.

The problem is we can’t contact SketchUp maintenance because our support is expired. Do you know how to contact them without purchasing a new maintenance & support license ?

That part is debatable. There are sometimes cases where we are the only people who can fix an issue, and so I did answer your support message from Tuesday morning. I sent my reply in the morning my time, with your now-should-be-working 2018 license.

Look for a message from prosupport@sketchup.com.

It looks like you haven’t replied to my support email yet, or come back since I posted last night. I will tag you, in case that makes the post standout better.

@AIG

I’ve seen your email today and now everything is working successfully, thank you very much Colin for your help

Great, thanks for the update.