Dunno about Gamebase 20, but remember that the adventures load into block 2+3, but the computer should be configured as unexpanded (typically by not using block 1). In VICE, it is easy to custom configure the RAM to block 2+3 and the load the program ,8,1. For some reason, attaching the file as a cartridge image starting at $4000 doesn't work for me.
If you're using a regular +24K expansion, you need to reconfigure the VIC into unexpanded layout. It can be done in several ways, but this is the least you need:
POKE56,30:POKE648,30:SYS58648 which will lower memory top, move the video matrix and blank the screen. Then you can load/run the game. SYS 32592 to start the adventure.
