You should check that you are setting your User-Agent to something unique and valid for your application. Fake (aka trying to impersonate a browser) user agent strings will get your application blocked. See https://wiki.openstreetmap.org/wiki/Tile_usage_policy

You should check that you are setting your User-Agent to something unique and valid for your application. Fake (aka trying to impersonate a browser) user agent strings will get your application blocked. See https://wiki.openstreetmap.org/wiki/Tile_usage_policy