The new interface is confusing because whatever you type is considered a single keyword.
For example, if you want to search for photos that include dogs and the beach, instead of typing "dogs beach" like you used to, now you have to type "dogs" first, at which point it shows a list of matching keywords under the search box which will include Dogs. Tap on Dogs and it converts your entered text into the matched Dogs keyword. Now you type "beach" and it will similarly show a list of matching keywords under the search box which will include Beach. Tap on Beach and it'll add it to the search box as a matched keyword. Now the results will show all photos that include both "dogs" and "beach".
If you just type "dogs beach" without tapping the matched keywords, it thinks you're searching for a single thing called a "dogs beach" which doesn't exist.