Seems odd, have you called call Sonos Support directly to discuss it? Are you up to date on your Sonos system, both firmware and the controller?

Have you tried restarting your phone or resetting the app? Have you installed the latest updates

The Alarms function is available for me:

I did all this. Actually this started when I moved to another house and took sonos from an old house. I reset all of the devices and updated everything then. It just disappeared.

According to this thread there is a known issue with alarms not showing and there has been no confirmation the issue has been resolved.

This issue comes and goes for me as well. I have been in contact with support (system diagnostic, asking what is connected to my wifi etc etc etc) but it has not been resolved.

Not exactly the same issue, in that I have the alarm option on my iPhone version of the App but unfortunately it doesn’t work, I go in and set an alarm and hit save and it momentarily appears on the alarm screen before disappearing. 

Alarms are configurable from my windows laptop and work perfectly well when set. Can even use the phone to turn them off (but I can’t edit them on phone, any changes disappear after hitting save)

I’ve contacted support but they weren’t much use, suggested I factory default all the speakers and delete the app and start again from scratch. Sounds a bit like the standard IT answer…. Have you tried turning it off and on again? Didn’t seem to want to get involved in what the actual cause of the issue is. 
 

Odd that they would suggest a full reset, if it is working from one device, and not the other. If I were to guess, it’s more likely to be a network communication error between the speakers and the errant controller device. I’d be tempted to actually delete the controller on the device that it is not working on, and then reboot that device. I’d then download a new version of the controller on that device. Check for any updates, and apply them, then go and look at the alarms. 

The controller itself is merely showing what is on the speaker(s), there aren’t any ‘alarms’ on the controller, so any alarms that are showing on one controller should be showing on all controllers. Well, within the Sonos app, I don’t want to speak about other things like alarms on Alexa or Siri, or Google. I have no idea where those are stored, 

A long winded way to say I think the issue is with the communication between your phone and the speakers…and since they’re working fine on your desktop, it suggests your phone is having trouble communicating properly with the speaker(s), in some fashion. Which, I suppose, could also be a mesh network issue, where the phone is connected to a different ‘node’ than your PC is…but that is a whole additional step. 

Thanks for your response, the IPhone App can see alarms that have been set on the speakers, it can even toggle them active/inactive. It can also be used to delete alarms. But it can’t create new alarms or edit the details (time, music choice, etc) of the existing alarms. 
Speakers and phone are all fully up to date, I have also tried deleting the app and data on phone but doesn’t make any difference. My next step will be to put the Sonos App on my son’s iPhone when he is round tomorrow, see how that behaves. 

Certainly worth a call to Sonos support to discuss it, then. If there’s a problem with their iOS controller, I’d bet they’d love to have some hard data to pass on to the coders. Like ​@ColinvZ has. 

Deleting the app and reinstalling it not making any change doesn’t terribly surprise me, the app is reading information from the speakers. 

Set up the App on my son’s IPhone and had no problems with alarms…. Now just need to work out a way to make my own phone work