No slider in Flash local storage

This problem started fairly recently.

When I play a particular Flash-based game, it pops up an error that says,

Your computer won't let your progress be saved. Right-click and choose Settings and choose unlimited.

So I right-click and choose Settings, and my options for local storage are Allow or Deny. (It's allowed.) There's no slider to change the amount of storage (as is shown on the various forums and websites).

I used the following website, which shows that this particular site is allowed 100 K of storage. Again, there's no slider to change the storage. The only slider is on the global storage.

http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html

So I changed global storage to unlimited and reloaded the site. It had unlimited storage. I reset the global storage (since I don't want everything to have unlimited storage) and my site is back to 100 K.

How do I give this website unlimited storage?

I'm running Windows 7, version 6.1.  I'm running Mozilla Firefox 65.0.2 (64-bit) (up to date) and Flash 32.0.0.142 (64-bit) (just updated). I cleared my cache and tried things again, and it didn't help.