I'm just here to explain why people pirate your software.
When I made the decision to buy VMware Fusion, I felt like it was a piece of software worth keeping in my personal toolbox for the rest of my life... that is the cost/benefit decision I made for it. I thought it was useful and it deserved my money. In return for my money, I'd be an owner of that software and would get the benefit of its future developments under the same product, with the same features I'd bought. New versions aren't expected to bring extra features. Just to keep working. Just like the app model of modern app markets.
Instead, what I got was a single, subversion-locked (8.5, not just 8, but 8.5) copy that doesn't even get updates, and not even a year later, I can't even open Fusion without being reminded that my purchase is now invalid, and I ought to go download (buy) the !NEW! version. And now, with Catalina, my Windows VM doesn't work - it launches with a black screen, boots up, even makes the startup chime, can be shut down and all, all with a blank screen. Just blackness. Like VMware's soul. Downloaded the latest Fusion, and, without asking (or confirming, or prompting), it overwrote my v8.5 app and asked me for a product key. I entered mine from the purchase confirmation, and it blithely spat in my face that "if you don't know what a product key is, why don't you buy one?". Except now I can't go back to v8.5 because it was overwritten without confirmation by just launching Fusion from the DMG.
Wow.
Trolls will blame the victim here, some kind of delusional thinking that I'm entitled for expecting a piece of software I bought - at considerable expense - to continue working for at least 2 years... not for it to crap-out after 2 years when the equivalent PC software (VMware Player) is 100% free for my use.
So, yeah, just here to explain why my next stop is a cracked copy of Fusion so I can actually keep using the product I paid for. Cheers.
Two things you can do to address this (one much easier than the other):
1) don't overwrite the app in the Applications folder without confirming. Especially not a licensed older version that will now be made invalid and unusable.
1b) when entering an older-version key into the key dialog, you really should be a little more polite about the message that it's not "valid". If you can detect it's from an older version, put yourself in that user's shoes for a minute and write a message that might lead them to want to pay you to upgrade. Don't just spit in their face with this "if you don't know what a product key looks like" garbage.
2) just make the licenses perpetual like people have come to expect from other software. Especially considering Fusion's position in what it does, compared to the free VMware Player, this should not be as expensive a product as it is with the limitations the license has. If you want to charge for every version, charge $15 for each version, not $90. You'd have a lot more happy people.