So I was planning to use Google Directions API in my application to plan transit routes in my city. The https request returns ZERO_RESULTS, even though Google Maps supports transit mode in my city.
And the same route planned with Google Maps
Is there any other way to solve this or any other APIs that I could use?
The Google Maps API is a separate product, so it is not the same thing as the Google Maps website or native app. Typically if you cannot find transit directions in the API that means Google doesn't have coverage for transit directions in API for certain area.
You can check where transit directions are available in your country using the following page:
https://maps.google.com/landing/transit/cities/#Europe
I cannot see Székesfehérvár in the list.
Unfortunately, I cannot suggest any alternative API.