I don't play flash games a lot. In fact, I try to avoid flash whenever possible; I just don't like the thing. However, there are a few games I like to play in my free time, like Amorphous+.

Lately (I can't tell you which OS it started happening on, but it happens on Sierra and it didn't happen, back when I was using Snow Leopard), whenever I restart my computer all progress made in those games disappears.

I understand these games save your progress by storing information somewhere on the computer's hard drive. If I right-click on the flash game, I get a contextual menu which includes the options "Settings" and "Global settings":

• If I select "Settings" and then go to the "Local storage" tab, the option to allow the website that hosts the flash game to save files to my computer is selected.
• If I select "Global settings" and then go to the "Storage" tab, the selected option is the one that says "Allow sites to save information on this computer".