Why am I unable to send an appointment link?

If you're using appointment links to invite patients, you'll have noticed there are reports like this in all the invite sections:

These reports are for patients who can be sent a communications annex, but can't be sent an appointment link. There are various possible reasons for this...

1. The patient can be sent an SMS but is unable to use appointment links, e.g. they've been recorded as unable to receive links on messages because they don't have a smartphone.
2. The patient shouldn't book themselves an appointment because of particular requirements, e.g. they need an interpreter to be booked. 
3. The appointment they need is more unusual, and so there isn't a report for that particular appointment link, e.g. as well as bloods and normal obs, they may need an ECG or foot check, or the blood test may need to be a fasting blood test and the patient be informed. In these instances, it's best if the patient calls to book these appointments to make sure they're booked correctly.