Zep, your front page HERE:

https://www.lexaloffle.com/pico-8.php

When I click on any of the games, the middle screen stays dark and does not load any game as intended.

I'm using Windows 10, 64-bit, Firefox Quantum v69.0.

If it doesn't work here chances are it doesn't work there for someone else. Thought I'd let you know ...

. . .

Solved. Just needed to clean the internet cookies for Firefox. Runs well here now.

Works fine for me
(Win 10, Brave v0.68.132 / Chromium v76.0.3809.132, 64-bit)

But agreed - others may be affected.

Hmm ... Could be the browser I suppose. Let me see ... Trying in Google Chrome. Works. Opera. Works.

Let me try one other thing.

Got it ! I cleared the internet cookies for Firefox. Hmm ... I haven't had to do that for lots of sites.Including the ones with Flash Games. Been a year or so since I last cleared my cookies.

Must be something tricky going on in the main page to present games like that.

Good. Was getting concerned it was something too complex to find.

Thanks for your help, Liquidream. Marked solved.