Install silo on WATCH (from iPhone's Watch App)—it may take a minute to show up on watch
Open SILO app on iPhone, and Allow Notifications (if not prompted, got to Settings > Notifications > SILO)
This typically works, when done in that order
If the above does not work, consider the following tips:
Make sure you are on the latest versions of iOS, watchOS, and SILO
Force quit silo. To force quit an WATCH app: hold the Dock button until power-off menu appears, then hold down the Crown
Be sure Notifications are Allowed: from iPhone go to Settings -> SILO -> Notifications -> turn on allow notifications. From the Watch app, go to Notifications -> SILO switch on. Also, scroll down and switch ON again to mirror alerts from iPhone
If your WATCH is loose on your wrist, it may accidentally lock (you may see a blue lock symbol on the top the of watch screen). When it's locked, notifications cannot go through
SILO will not work if iPhone/Watch is in "Do Not Disturb" mode—(it will work in Airplane Mode)
Consider increasing Haptic Strength: from WATCH go to Settings -> Sounds & Haptics -> increase Haptic Strength. Or turn on "Prominent Haptics" for an extra tap
If you are using Bluetooth headphones via WATCH during a session, it could suppress the haptics.
As a last resort, you may have to do a Restore and Backup of your WATCH