I am testing the upgrade from Moodle 3.3 to 3.5 on a test server. Everything has gone well except for the WIRIS math plugin. I installed the three plugin source files into place (from WIRIS) prior to running the upgrade. I get this message when viewing the WIRIS plugin settings page -> Site Admin/Plugins/Filters/MathType by WIRIS.
but they are installed. When I search for wiris directories from the moodle install path I find:
$ find . -name *wiris
./filter/wiris
./filter/wiris/integration/lib/com/wiris
./lib/editor/tinymce/tiny_mce_wiris
./lib/editor/tinymce/tiny_mce_wiris/tinymce/generic_wiris
./lib/editor/atto/wiris
./lib/editor/atto/wiris/generic_wiris
$