I bought SketchUp Pro 2017, and I haven’t updated the software up until now as I wasn’t sure if in doing so, I’d have to pay again for it. Or is it simply an update of the 2017 that I bought and I won’t have to pay any lump sum or ongoing fee?
Go to the following link, enter your information and you should be able to find out what it’ll cost you to upgrade. Since you haven’t been keeping your maintenance and support up to date, I expect you’ll just pay the $299 for the subscription for 2021. But check at the link to make sure.