Your RBZ archive, (the extension registrar script and your extension folder) should all begin with your developer name, not “extension”. (It is already implied that an RBZ archive contains an extension.)
You did not follow the instructions.
The name of the RBZ should be the same as your extension subfolder with a version number added. (You left the RBZ named “Basic”.)
Example:
"Author_ThisPlugin_v1.0.0.rbz"
… but"Author" changed to your company name, and "ThisPlugin" changed to your plugin name.
The registrar script name and the extension subfolder name need to be this base name (without the version number.)