Can I upgrade from lite to SP Page Builder PRo?

Hi,

Yes you can. You will get all related info there:
https://www.joomshaper.com/documentation/sp-page-builder/sp-page-builder-3#basic6

And please make sure you have input your email and license key to SP Page Builder -> Pages -> Option (on the right) -> License & Update (input your email and license key) -> Save and Close. and then clear your browser and Joomla cache.

Most importantly, You have to copy the license key from your Joomshaper Dashboard. I have attached a screenshot for your ease:
https://prnt.sc/vesh66

Hope it helps!

Best Regards