Since the user guide doesn't actually say this, I had to do a lot of digging to figure this out. In the launcher at the bottom left (on Java version) it says what version you are launching. If it says "Snapshot" then you won't be able to launch the tynker server. Make sure it does not say snapshot and instead says the latest version number. It should read something like Minecraft 1.1.14 (that isn't exact but it something along those lines).
If you launch the version that says "snapshot" in the version it will tell you the tynker server is out of date.
Once you launch the most recent version of the Minecraft go to multiplayer and re-type in the server. Make sure to go into OPTIONS before joining and select the resource that isn't plain Minecraft. It needs to be in the left box.
The guide says nothing about the version needing to be a specific version, and i see the "helpful" comments instructing everyone to just read the guide which doesn't say anything about making sure you are opening the correct version. If other parents are like me and have never used Minecraft on PC, I had no idea i couldn't just launch and join and was beginning to get very upset. I almost quit when i found on google about an entirely different server, that one has to make sure the MOST RECENT version is selected BEFORE launching. I don't know what "snapshot" version is, but it won't let you join the server so make sure it doesn't say "SNAPSHOT" in the launch menu.