1. Enable Enrolment on payment plugin (just enable, don't change any other settings)
2. Create a course and go to Enrolment methods page for it
3. Select Enrolment on payment from Add method dropdown
4. Try to save the form without changing anything (by default Allow enrolment is set to Yes)
5. You will see error message Enrolments can not be enabled without specifying the payment account and form is not saved
6. Change Allow enrolment on payment enrolments to No and Save changes
7. Form is saved and enrolment is disabled
8. No click enable icon for enrolment on payment instance
9. Instance is enabled, but there are no account available

So saving form when Enrol on payment is not allowed leads to bypassing check of Enrolments can not be enabled without specifying the payment account