Thanks, I didn't test the plugin on old Minecraft versions. You can expect a fix in a new update.
Sign Shop is enabled by default. You would need to place a sign and write on it:
1. [cbuy] or [csell] or [abuy] or [asell] <- On the first line of the sign (This can also be changed in config.yml)
2. amount (Example: 10)
3. material name (Example: apple)
4. price (Example: 0.001 btc)
You can add me on Discord: Crazy Rabbit#0001 for easier communication.
Edited: Quick fix has been applied. Older MC server versions don't support getBlockData(). So Sign Shop won't be enabled on older MC server versions as of now. Other crypto functionality should work.