Hi there,
This is a known issue that several Apple Watch users have experienced after updating to watchOS 26. The Weather and Messages complications have been reported as missing from the Modular and Infograph Modular faces. Here are a few things you can try:
1. Re-edit the watch face: On your Apple Watch, press and hold the watch face, tap "Edit," swipe to the complications screen, and tap on each slot. Sometimes the complications that seem missing will reappear in the list. Scroll through all the available complication categories carefully.
2. Make sure the Weather app is installed on your iPhone: The Weather complication won't appear as an option if the Apple Weather app has been removed or isn't available. Go to your iPhone's App Library and search for "Weather." If it's not there, download it from the App Store.
3. Check Background App Refresh: Go to the Watch app on your iPhone > General > Background App Refresh, and make sure Background App Refresh is turned on for the Weather app.
4. Try setting the watch face from the iPhone: Open the Watch app on your iPhone, go to Face Gallery, find the Modular Infographic face, and add it from there. You may be able to assign Weather and Messages complications when adding it fresh.
5. Unpair and re-pair: If nothing else works, you can try unpairing your Apple Watch and setting it up again. Some users have reported that setting up as a new watch (rather than restoring from backup) resolves the complication issues after a watchOS 26 update.
6. Contact Apple Support: Since this seems to be a widespread issue after the watchOS 26 update, it may also be a bug that Apple needs to address. Consider reporting it through the Feedback Assistant app on your paired iPhone.
Let us know if any of these help!