Starting 1.18 version we have new search types that require additional settings from Theme Options-Search-Advanced Search Form.
These are the options that can be found in Advanced Search form section:
1. Use Custom Fields For Advanced Search
2. Number of Search fields to show in search
With this option, you will be able to set how many fields will be included in the Advanced Search form.
3. Set custom fields for search
First, you need to select the number of fields and press Save changes button. After the first save, the custom fields list will modify according with number that you added. If you select 5 fields, after save, this is how the list will show
The next step is to press Save Changes button again, so the change show on front end as well.
3. No of Search fields per row
The maximum number of rows supported on the search form is 4, but you can also select 1, 2 or 3 fields.
The custom fields we support must be set with correct COMPARE. Read here about all the options that can be added to search: