Can you please try below way once:

 val now = "2025-06-13T15:00:00.000+01:00"
 val mockedDateTime = ZonedDateTime.parse(now)
 val clock = Clock.fixed(mockedDateTime.toInstant(), mockedDateTime.zone)
 Mockito.mockStatic(Clock::class.java).use {
     it.`when`<Any> { Clock.systemDefaultZone() }.thenReturn(clock)
     // call api
 }

Import Clock from import java.time.Clock;