i want to help people who come across this issue

the Default.sgl file is missing from summer games.

First time you try to run the tournament it will ask you to insert the torunament disk. Press ESC and navigate to the summer folder, press open. It will create a summer.sgl file. Now navigate to the file and press enter.

You should be in the tournament menu.
Hope this helps someone.

Thanks!

Odd that it wasn't set up properly, though I guess it might be because it was published by Piko Interactive. They never seem to make any kind of effort for their releases, here or on Steam.

Thanks, this was really useful :)

I found an alternative process to fix this: you must remove the SGDEF.BIN file inside the Summer Games installation.
Removing that file will cause a Setup screen to appear when launching the game. You just need to click OK or press Enter. It will send you to the main screen, and then you can start a new tournament without any issues.