@Asriel
I have encountered this problem before, try installing the 2 texture packs; Wacky Worlds and Time Twister. You can buy these at places like Amazon, Walmart, etc.
If that doesn't work, please direct to your OpenRCT2 installation and open "openrct2,com" (not a link). If the game starts as normal, join a server you normally can't join and take a screenshot of the .com file.