Hi Ken thanks for posting in the Lucid community - I'm happy to help! Unfortunately even though the URL exists within your Google Sheet as a hyperlink Lucidchart will treat the URL as regular text and clicking on the text to open the link is not currently supported. However you might find this video helpful - it walks you through how to assign the hyperlink as an action for that shape in a really simple way with a "clickable" final result.
However we're always looking for ways to improve Lucidchart and your feedback is the best way for us to do that. I certainly understand how it would be helpful for the URL to import directly without needing to set up an action. Would you mind adding your idea to Product Feedback space? Ideas submitted here are visible for others to upvote and comment on, and are passed on to the product development team for their consideration. As a growing company we take our feature requests very seriously. Thanks for your request and apologies for any inconvenience.