Hi,
Some time ago I bought an LRT version 5 PRO with a license key. Currently I have upgraded to version 6. Unfortunately, that key does not work. Should I buy a new license?
Ryszard

If you want to use LRTimelapse 6, you'd need to upgrade your license key. There are discounted upgrades on https://lrtimelapse.com/upgrade/

Thank you for answer

Hello Gunther,
I have LRTimelapse 5Pro and purchased 6 Pro upgrade. Please provide instructions to upgrade. I am using MacBook Pro M2Max.
Do I have to trash the version 5 Pro and download version 6? Do I have to clean Library and Software Support folders? Do I have to re-connect with the latest Lightroom Classic? Thanks

Nothing to do apart from just closing LR and LRT (as with any update).
Then download and install the latest version from https://lrtimelapse.com/download/
Launch it and activate your new license as described in the email that came with the license.