Please, check the following:
1. The filter option must be added in your Filter Menu admin. If you didn't add the filter to the filter group in your Power Tools admin it won't appear on the frontend.
The filter option must not be hidden (in the case it is hidden, click the 'eye' icon to unhide it).
2. There must be matching products for that filter in the source collection. Filters are collection based, and if there are no products/results to show filters won't appear.
Quick way to check - click on the 'Source' for the filter that doesn't appear on the frontend - it will open associated collection, check the collection has products in it and those products are not hidden.
3. The collection must not be hidden or unpublished. In the case the collection is hidden you should see this message for the missing filter.
4. You have too many tags in use.
Shopify has limits on the number of tags that are returned on any page - it will only return the first 1000 unique tags. If you exceed this number then the tags get truncated down to the first 1000. The filter menu uses these tags to generate the filters and if you have many tags that are not being used to filter then these unused tags will take up the available spots and the actual items you want to be filtered on will not be seen.
The solution is to make sure you only add tags for items you plan on filtering on, and superfluous tags should be removed.
You can view all the tags by going to any product in the Shopify admin, then pressing View All in the tags area. You can copy this list to Excel or other spreadsheet program, clear the tags you want to keep, then go to Power Tools -> Bulk Edit Tags, and paste the list of tags to be deleted into the Bulk Delete Tags box.
If there is further issue with this, please, email us, we'll be happy to send a store access request and check!