Your only hope is to fully charge the Nuvi 205 and then place it outdoors away from buildings, trees etc. for as long as possible, obviously this has to be done on a dry day as the unit isn't waterproof. Your unit has an internal oscillator that is used to 'sync' with the satellite signals, but if it is too far from optimal, it won't get the signal in the first place.
If the unit won't operate on it's internal battery, it's posible that replacing the battery could fix the problem because a faulty battery can affect the unit's performance even when powered from the USB conector, to try this out you could disconnect the internal battery and power the unit via USB, if this gets a satellite 'fix', then you need to replace the internal battery