So, there's a few things to check: As you mention web clips, I assume Apple devices?
1. APNS: Check that your APNS cert is still valid: Organisation > MDM
2. If that's all good, pick a device that you know to be good from the device list and click on it. Scroll down to Online Status : What's the status?
3. Scroll down to your Activity log: when was the last time the device(s) checked in?
4. Go to Organisation > Change Log Have a look to see if any changes were made (especially around WiFi, as @BlakeRichardson mentioned )
Report back with your findings.