All set now. For others reading this thread, I emailed support following Barry’s instructions.
Purchased a new Events Calendar Pro, using the discount code provided via email from support.
Wasn’t able to do an automatic update via WordPress back end, so downloaded the zip file from my Modern Tribe account download list.
Then uploaded via WordPress back end – plugins > upload new plugin – checking “Yes”, this is an update to a current plugin.
Then replaced the old license number with the new license number provided via purchase confirmation email. Plugins > The Events Calendar Pro > Settings > Licenses