Why would God, who is eternal and everywhere, set a 'time' for when He can be found?
This verse isn't about God's presence changing, but about our receptiveness. 'While He may be found' speaks to the opportune moments God provides – times when His Spirit is actively drawing us, His Word is speaking clearly to our hearts, or His grace is readily accessible through His people and ordinances.
Think of it as a special invitation. God is always God, but He makes Himself particularly available and receptive to us in specific seasons. To miss these moments isn't because God moves away, but because we, through stubbornness or neglect, close ourselves off. The urgency is for us to respond now, while the door of grace is wide open.