Probably, you did not define the capture template your browser extension/bookmarklet expects (it's usually a single letter). You may look at https://github.com/sprig/org-capture-extension/issues/1 for hints how to solve the problem.
Best, Ihor Jean Louis <bugs@gnu.support> writes: > I have started using Org-capture but now without changing Emacs > session it stopped working with error: > > Greedy org-protocol handler. Killing client. > No server buffers remain to edit > > Do you know any how why this happens?