How do I tell which one it is?

Signups tell you about the first two. Completion rate tells you about the second two. If people are joining and not finishing, stop looking at placement.

How long before I should worry?

Give it long enough for a typical regular to have had several chances to visit. Judging at two weeks tells you about signup, not loyalty.

Why nobody is using your loyalty programme

Most likely, in this order: your staff are not mentioning it, the code is somewhere nobody stops, the reward takes too long to reach, or the reward is not worth having. Three of those cost nothing to fix. None of them is the technology.

Almost always one of four things, and they are diagnosable in a specific order.

First: is anyone mentioning it?

The single largest factor. A programme nobody says out loud is a poster.

Test it by standing near the counter for twenty minutes. If it is not mentioned in that time you have found your answer, and you have not needed any data.

Second: where is the code?

It has to be where somebody is standing still with nothing to do. Counter, table, pickup point. On the door, on a wall behind the queue, or on a leaflet is close to not having one.

Third: is the finish line reachable?

Divide your threshold by how often a regular visits. Over about six weeks and most people stop counting.

This shows up differently in the data: people join and then stop. If signups are healthy and completion is not, it is this or the next one.

Fourth: is the reward worth having?

The rarest cause, and real when the reward was an afterthought. The test is whether a customer would describe it to a friend unprompted.

The diagnostic order matters

Signups diagnose the first two. Completion diagnoses the second two.

Owners tend to reach for the threshold first, because it is a number they can change from a screen, and it is the third most likely cause. Check whether anyone is mentioning it before you change your economics.

What is almost never the cause

The technology, or customer reluctance. People join things at counters readily when a person asks them. They do not join things nobody mentions.