The schedule is stored on the diffuser itself. So it should also turn on when the app is closed and your phone isn't nearby. If it stays silent, check the following.
1. Is it set to On?
Open the app. The round on/off switch next to your diffuser should be black (On). If it's set to Off, it will skip its schedule. Tap the switch; below the day bar you'll then see something like "Your diffuser starts today at 17:00".
2. Does now fall within a time block?
Look at the day bar: if the marker for now falls within a black block, it should be spraying now. If not, it's simply not scheduled time. A diffuser also sprays briefly and then pauses for a few minutes; that's normal.
3. Smart Aroma Diffuser Pro: is the button set to Smart?
If the timer button is set to 1H, 2H, 4H or 8H, it runs via the button, not via the schedule. Set it to Smart. Do you have a Pro from a recent shipment and the schedule doesn't work, or does it spray non-stop? Read Pro sprays non-stop or the schedule doesn't come through.
4. Is the clock correct?
On the diffuser page, tap the gear icon and choose Sync clock. The schedule follows the diffuser's own clock.
5. Is there actually a schedule?
If Schedule shows not set yet, choose a schedule; see Setting up a schedule. If you recently installed the new app, you had to pair once again; you could take over a schedule that was already on the diffuser during that process.
6. As a last resort: reset
If nothing helps, reset your diffuser and set it up again. Smart Aroma Diffuser: see Resetting the Smart Aroma Diffuser. Pro: hold the on/off button for 5 seconds. Smart Aroma Diffuser 2: unplug it for 2 minutes.
Still not working after that? Contact our customer service and ask for a team member. We're happy to help further.