What this problem is
After changing themes, the header menu is missing or shows the wrong items.
Why it happens
- Menu locations are theme-specific
- Block themes use Navigation blocks instead of classic menu locations
Prerequisites
- wp-admin access
Diagnosis
Check if the menu still exists under Appearance > Menus (classic) or in the Navigation editor (block themes).
Detailed steps
Step 1) Reassign menu locations
Appearance > Menus > Manage Locations: assign your menu to the new theme locations.
Step 2) Block theme: check Navigation blocks
Appearance > Editor: open Header template part and ensure a Navigation block exists and points to the correct menu.
Step 3) Clear caching
Purge caches after changes.
Expected results
- Menus appear again on the frontend
What to do if it fails
- Check if a page builder overrides headers
- Switch to a default theme to confirm whether it is theme-specific
Best practices
- Before theme changes, export menu structure and note menu locations