Installing and upgrading help

You are right Howard, adding this statement caused another problem. I am now unable to enrol users in a course. When i remove the statement, i would be able to enrol users but then can no longer create users. When i turn debugging on, the message says:

Debug info: COLLATION 'utf8_bin' is not valid for CHARACTER SET 'utf8mb4'
SELECT 'x' FROM mdl_user WHERE LOWER(email) COLLATE utf8_bin = LOWER(?) AND mnethostid = ? AND id <> ? LIMIT 0, 1
[array (
0 => 'cynthia@ceelearningsolutions.com',
1 => '1',
2 => 3797,
)]
Error code: dmlreadexception
×Stack trace:
line 486 of /lib/dml/moodle_database.php: dml_read_exception thrown
line 1188 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->query_end()
line 1918 of /lib/dml/moodle_database.php: call to mysqli_native_moodle_database->get_recordset_sql()
line 1903 of /lib/dml/moodle_database.php: call to moodle_database->record_exists_sql()
line 310 of /user/editadvanced_form.php: call to moodle_database->record_exists_select()
line 607 of /lib/formslib.php: call to user_editadvanced_form->validation()
line 543 of /lib/formslib.php: call to moodleform->validate_defined_fields()
line 653 of /lib/formslib.php: call to moodleform->is_validated()
line 171 of /user/editadvanced.php: call to moodleform->get_data()

What do i do now? This is frustrating.

I am also experiencing another issue which i am going to post as a new topic.