Updating Clean Journal Pro – error

HI. I saw in my wp-admin dashboard that there was a new version of clean journal pro available. I selected and clicked to update but got an error message instead. Wondered if you could tell me how to fix so i can update the version i have. Please see below. Thanks. - martha Update Available There is a new version of Clean Journal Pro available. View version 2.8.1 details. Automatic update is unavailable for this theme. I also have custom css in my theme customize. Will i lose that with the update?