Here is the error which appears in the text area after I click on the wysiwyg link from sandbox on twiki website.
TWiki detected an internal error - please check your TWiki logs and webserver logs for more information.
Can't locate HTMLpath in
@INC (
@INC contains: path path-linux-thread-multi/ path path path . path-linux-thread-multi path path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path path path path path path path path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path-linux-thread-multi path path path path path path path)
You need to install HTML::Entities.
This is a problem in your configuration, not a TWiki bug.
CC