I turned debug on and tried again.
Coding error detected, it must be fixed by a programmer: Request for an unknown renderer class core_webservice_renderer
More information about this error
Error code: codingerror
Stack trace: •line 299 of /lib/outputfactories.php: coding_exception thrown
•line 1500 of /lib/outputlib.php: call to theme_overridden_renderer_factory->get_renderer()
•line 779 of /lib/pagelib.php: call to theme_config->get_renderer()
•line 46 of /admin/webservice/service.php: call to moodle_page->get_renderer()
I searched the files of moodle-latest-26.
The string "webservice_renderer" is not found anywhere.
What could be wrong? How do I fix this?