The trade range was recently increased in Pokémon GO. Read on below to learn more:
Limited-time test: Trade range increased until Monday, November 16, 2020, at 10:00 a.m. PST (GMT −8)
As a limited-time test, from Thursday, November 12, 2020, at 2:30 p.m. until Monday, November 16, 2020, at 10:00 a.m. PST (GMT −8), trade range will be increased! Depending on information gathered from this test, we may include increased trade range as a part of future events.
It’s time to trade, Trainers!
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—The Pokémon GO team
Source: Official Pokémon GO blog