Most likely the frontend is working on the previous (outdated) CSS files. To avoid such cases, always clear the static content cache after making any backend changes (to the platform or an extension).
If the problem remains, you can check the browser console for errors (for example, in Chrome this will be Developer tools / Console).
Also, you can try following Magento 2 template page hints.
- Login in Magento Admin Panel.
- Click on System and select Configuration option.
- Click on Advance and select Developer option.
- Select Debug tab and Enabled template path hinds for store front.
Save the configuration and clear the cache.
