This game has 2 types of fuel.
You have built an AVGAS fuel depot, but medium aircraft use JET A1. Which is another fuel depot
Make sure you buy it under Procurement.
Hover over the fuel depot build icon and you will see the choices you have.
Your first screenshot confirms you have AVGAS enabled, so small aircraft should be able to get fuel.
If it doesn’t work (because the text after it does look strange ) try saving and reloading.
If that doesn’t fix it, file a bug report
Actually the Cessna 208 does uses Jet A1 as it has a turboprop engine so its not a bug/over-simplification. As for the issue I had the same multiple times, only fix seems to be unlocking jet and avgas.
Heres the simple way: When you unlocked avgas their should have been jet1 fuel at the bottom. You will have to unlock it for 100,000 and build a new fuel depot for it. Then you can finally set it on
The same glitch just happend to a safe of mine turns out that it seems to happen when you unlock fuel service and the fire to procurement director. I’ll see if I can reproduce it later on