If you see failed status on the invitation it can mean 3 things:
There is, however, a workaround, if you are absolutely sure the email address is correct. If you open Course/Participants and scroll down to "Sent invitation" panel, you will see an icon with 3 dots next to each "Failed" message. Clicking it will open a menu where you can select "Resend". This will launch an email client and will put invitation URL to the message. This way you can send invitation URL to the student from your own email account (or deliver it in any other way). Sending from a personal account naturally overcomes spam filter problem.
- There is a typo in the address (for example extra dot or "m" missing from .com)
- The student has closed email account entirely, thus, it does not exist in the mail server anymore and any emails send there will be bounced back with "failed" message
- The student has marked notifications from Eliademy as spam. In this case, our mailing server stops sending emails for some time knowing they will never be delivered anyway.