お疲れ様です！

タイトルの通り、Google Places APIで近くの飲食店を探す際、
半径に大きい数字を入力するとZERO_RESULTSが返却されます。
公式ドキュメントには、50kmが上限であると記載がありました。

The maximum allowed radius is 50 000 meters.

現象

https://maps.googleapis.com/maps/api/place/nearbysearch/json?key=***&location=35.6980864,139.7663461&radius=10000000&language=ja&keyword=(food OR restaurant OR cafe OR meal_takeaway OR meal_delivery OR bakery OR bar OR night_club) "上島珈琲店ワテラス"

result.json

{
   "html_attributions" : [],
   "results" : [],
   "status" : "ZERO_RESULTS"
}

修正

6,000kmくらいでもいけましたが、場所によって取れたり取れなかったりするので、素直に50kmを指定しましょう。

https://maps.googleapis.com/maps/api/place/nearbysearch/json?key=***&location=35.6980864,139.7663461&radius=50000&language=ja&keyword=(food OR restaurant OR cafe OR meal_takeaway OR meal_delivery OR bakery OR bar OR night_club) "上島珈琲店ワテラス"

result.json

{
   "html_attributions" : [],
   "results" : [
      {
         "business_status" : "OPERATIONAL",
         "geometry" : {
            "location" : {
               "lat" : 35.6976308,
               "lng" : 139.7680488
            },
            "viewport" : {
               "northeast" : {
                  "lat" : 35.69898062989273,
                  "lng" : 139.7693986298927
               },
               "southwest" : {
                  "lat" : 35.69628097010728,
                  "lng" : 139.7666989701073
               }
            }
         },
         "icon" : "https://maps.gstatic.com/mapfiles/place_api/icons/cafe-71.png",
         "name" : "上島珈琲店 御茶ノ水ワテラス店",
         "opening_hours" : {
            "open_now" : true
         },
         "photos" : [
            {
               "height" : 5248,
               "html_attributions" : [
                  "\u003ca href=\"https://maps.google.com/maps/contrib/100183066775808774145\"\u003efoamer styro\u003c/a\u003e"
               ],
               "photo_reference" : "CmRaAAAA8hwm924MRve3ZPpRIy0F3UdBRRYq1ILazjtCKfuMLfuevEi9Y-MjGSJmowhxd37Io7e6d0NG_ZY0g6osqTaFfCvgiNxDwrWcAoLtK30k1N0ZRY0yJIjYHETOqmF89EwFEhBW8UVL_m65NRYBRSHZI3TwGhTrnSdPAkxoALobuthwImYyaKE4FA",
               "width" : 3936
            }
         ],
         "place_id" : "ChIJraztWRuMGGARZ69grx11sMs",
         "plus_code" : {
            "compound_code" : "MQX9+36 千代田区、東京都",
            "global_code" : "8Q7XMQX9+36"
         },
         "price_level" : 3,
         "rating" : 3.9,
         "reference" : "ChIJraztWRuMGGARZ69grx11sMs",
         "scope" : "GOOGLE",
         "types" : [ "cafe", "food", "point_of_interest", "store", "establishment" ],
         "user_ratings_total" : 194,
         "vicinity" : "千代田区神田淡路町２丁目１０５ ワテラスアネックス1F"
      }
   ],
   "status" : "OK"
}