This on a Mac mini M1 using Parallels 18.1.0. Being notified about an upgrade to 18.1.1 and pressing "Download update", the download fails immediately with "The file 'ParallelsDesktop-18.1.1-53328.dmg' can't be downloaded. Try again later." (error message translated from german by me). Tried this on two different days, no change. And just in case: no, internet connectivity isn't broken on my end. I am posting this from the same machine, that fails to download the Parallels update.
Greetings! Thank you for this message provided. We've created a ticket in our system to proceed with investigation of your issue. Kindly check your inbox or in my.parallels.com. Just login > find "Support" tab in the top-right corner > My tickets. Thank you!