I opened my browser and opened minecraft and i found 17w06a and i tried but it didn't let me use it it wasn't on there

We are unable to diagnose your issue due to the lack of proper debug information. Please review the guidelines before reporting issues.
In case of a game crash, please also attach the crash log from [minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/finding-minecraft-data-folder].

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